Scaling the Imperium

By Lightbringer, in Rogue Trader

Does any one else think it seems a little ludicrous that the imperium would use space transport to bring food to hive worlds? Not because ships can't carry enough food. It just seems the warp is a little unstable.

I think space transport would be reserved for highly precious material such as nephium ad promethium which can't be found on most planets.

I figure hive worlds could have orbitals they use for agriculture. As well as recycling plants and algea plants.

May be they ship ust enough fertilizer to keep the on planet farms running rather than actual grain and meat.

I think you're right to a degree - warp travel is clearly very dangerous. However, the very existence of agri worlds is suggestive that they are necessary. While it is no doubt true that the Imperium possesses the technology to construct orbital farms, I can't recall seeing many references to such things. The world of Precipre is the only one that springs to mind that is similar.

I would hazard a guess that most of the risk of warp travel comes from travelling to unknown regions through parts of the warp that are inherently unstable. Travelling along well known warp conduits making tiny computer calculated jumps, in the manner of most of the chartist captains, is probably much less risky. I imagine a realtively stable command economy could be built around travel like this.

In terms of how most Hive worlds deal with food shortages, though, I reckon they eat dead people, ieatdeadpeople2. Corpse starch rations all the way! :)

Hahaha ya "It's people! Soylent Green is people!"

As a science student I love thinking about these kind of social engineering problems the imperium would face

So here's what I'm thinking. There's really 2 possibilities here when i come to food supply.

1) The Imperium has existed long enough to know and have learned that out of sheer necessity it has to run in a sustainable manner which will detail below as well as support from cannon that it operates like this. I ind this to be a more interesting option but honestly both are equally likely

2)The Imperium is the exact same as most societies in history. It leaches what ever it can as fast as it can. Its basically ****** the galaxy for all its worth because it knows it can or because its just concerned with day to day survival.

Sustainability

I've always pictured the Imperium to ironically be a rather tolerant society in certain ways. According to Imperial compliance genocide of any human population is prohibited suggesting racism is a thing of the past. Based on the number of females in command position in various cannon sources sexism is probably much less prevalent. Not on all the planets the Imperium controls but the interstellar government itself is probably rather tolerant. Here's another way it could ironically have aspects we desire in our own society.

Bellow is my argument that the Imperium is an ecologically sustainable society.

The Imperium has existed for 10 000 years and it has 30 000 years of history to draw upon even if it fragmentary.

In this time it has seen planetary ecologies collapse and they know that for the Imperium to continue existing for all eternity they need to keep a steady food supply. That being said they have access to multiple planets so not all of them need to have their ecologies protected. Certain worlds, such as hive, mining or forge worlds have to much mineral wealth or work-force wealth to be useful as food providers any way. By relegating industry to these places they can effectively control the pollution keeping it in its own little Petri-dish.

Agri-worlds are not what you think they are. They are effectively nutrient factories, they use them to produce vital nutrients for the populations of forge and hive worlds to remain productive. The Imperium doesn't just factory farm these planets because that would suck out all the nutrients, just look at the middle east. Instead it creates efficient crop rotation cycle that ensure a source of food that can support hive worlds for thousands of years to come, it only takes as much of the crop as a hive world needs to support is corpse starch rations.

I think this argument is logically sound and hive worlds are described and being efficient with food as possible why not other parts of the Imperium as well?

Unchecked Growth by Necessity

2)The Imperium is an empire of a million world. But that being said according to the drake equation which was discussed earlier the galaxy has billions of worlds and the Imperium knows this. The Imperium needs food now and as much food as it can get its hands on so it can foster growth. Sustainability wont foster growth now. We need more of everything to wage war eternal better, faster, stronger, and most importantly bigger than our enemies which are everywhere. Sure the Imperium needs to exist eternally but there are billions of other worlds out there to use. Even in sectors which are untouched by a major war they need resources form these places to support other major crusades and defensive fronts.

This theory does fit with the general mentality the Imperium puts out. Hive worlds are only super efficient because they out of necessity have to be but this does not necessarily imply that the Administratum or the Adepta Terra in general shares this mentality. Also very few human societies have ever been sustainable (at least on one planet). And if history shows us one thing its that humans don't learn anything from history.

Edited by ieatdeadpeople2

sorry for the long post

Also they probably do ship some real food. The super rich and middle class of a hive world is still a massive market that is willing to pay exorbiantly inflated prices for real meat and grain. Even if only 0.01% of Scintillas population lived a life that would be considered middle class in the western world (good safe job with benefits like owning a manufactorum or being a supervisor there) that's still 2.5 million people demanding real food everyday at massively inflated prices. Easily a market for a rogue trader or chartist captain to exploit.

Edited by ieatdeadpeople2

The thing I would be interested in seeing you calculate would be the total mass that the merchant fleet could trade between worlds regularly. If we know how many ships they have, and we have a decent idea of how big each ship is (the Vagabond for example), I'd be curious about how much stuff actually gets shipped between planets each year based on those numbers.

That's a big ask! :) I agree it would be nice to see some figures on this, but I wouldn't really know where to start!.

... :D

I couldn't help myself, it was just too interesting a question. Here's phase one on my end:

I’ll pull one of my cargo transports out (the Imperial Providence ), since I think it’ll serve as a good stand-in for a generic hauler in the Imperium. She’s a Jericho-class Transport, with Gellar field, Void Shield, Warp Drive, Commerce Bridge, M-100 Augurs, 2x Thunderstrike Macrocannons, 1x Mars-pattern Macrocannon, and 2x Main Cargo Holds.

In a quieter part of the Imperium than the Koronus Expanse, I could see the shipyards only putting on a single Mars-pattern or Thunderstrike Macrocannon array, giving it one more Main Cargo Hold.

With 3 Main Cargo Holds, that brings the total cargo area to 78million m3 storage space.

Taking out 10% for things like load equipment, bracing, servitor storage, and giant statues of the God-Emperor, that leaves a ‘typical’ Jericho-class Transport with 71million m3 of storage space. How much is that?

Well, with a quick search for some equivalents, we can find that a standard shipping container is 77.02m3, and that the largest cargo ship currently active (according to Wikipedia) is the Maersk Mc-Kinney Moller which holds 9,135 of our 40ft cargo containers (for a total of 703,577.7 m3).

Judging by that, the Imperial Providence can transport almost 101 Maersk McKinney Moller ’s worth of cargo.

That’s a lot.

So, as a quick judge of scale, how much food could the Imperial Providence in full cargo-mode transport from an agriworld to a Hive World? That’s going to take a bit of back tracking.

Because it sounds fun, lets use an Imperial Bushel of wheat as our base unit (~36 liters, or 0.036m3). That means the Imperial Providence can carry just under 2 billion (yes, billion with a ‘b’) bushels of wheat.

The average American (according to the USDA) eats 200 pounds of grain per year, which is about 3.3 bushels. To make that even, 10 bushels of wheat could feed 3 Americans for a year (with a bit of protein thrown in!).

What does that ultimately mean?

Each trip, the Imperial Providence would carry enough grain to feed more than 600 million Imperial Citizens

Even with the vagaries of the warp, as long as the planetary governor made sure to stockpile the first 10 transports that came in, he could easily feed an average hive planet for a year (or more, with proper rationing and reclamation procedures).

As an aside, that means that a typical Imperial Transport ship can carry the entire grain production of the United States each year in one trip… talk about efficent.

Edited by CaptainRemiVandigrath

Impressive CaptainRemiVandigrath! So it is possible to carry that much but you have to keep spoilage in mind

SO america currently loses 40% of its food supply to spoilage each year ( http://www.nrdc.org/food/files/wasted-food-ip.pdf ). And transport in modern times is much faster than it used to be. Transport time in the 401st mellenium is about equivilent to age of sail transport times.

I think we could be looking at between 60-50% spoilage. So each Imperial providence would actually only be providing for 300 million citizens.

By this estimate Scintilla (pop 25 billion) requires 84 (rounding up) imperial providences to arrive each year.

Necromunda would need 256 imperial Providences a year to feed its hives. But necromunda is probably one of the largest hives in the galaxy so its not unrealistic

Does anyone want to try to work out a realistic estimate of the amount of transports in a merchant fleet to support a sector?

Still doable I agree as long as there are enough ships to carry that much. So great the Imperium can function in terms of food transport. So that does away with my argument that we only transport fertalizer's for algea farms.

But we have yet to consider if the Imperium can produce that much food from its agri-wolrds does any one want to work out the amount of ariable land?

This will basically determine which of the two strategies I outlined above the Imperium uses to feed it's citizens.

Edited by ieatdeadpeople2

My room mate did also point out to me that a lot of the spoilage that occurs in modern america is actually due to people just throwing out off color or irregularly shaped food. Food that more desperate people (lower class imperial citizens) would eat.

So I don't actually know how accurate my numbers above are.

Does any one here know how to work that out? Are any of you sustainability or history students?

Keep in mind that what we're trying to work out here is spoilage that would occur given modern (or better) preservatives and refrigeration technology but requiring an age of sail time to go from farmers field to the mouths of citizens.

We also need to know the size of our merchant fleets has anyone worked that out yet?

Edited by ieatdeadpeople2

OP, I applaud your conclusions which are almost entirely based on guesswork and impartial information. Yes, "it fits."

Interesting note: the World Health Organization says that an average person requires 2,100 calories per day to live (listed as a requirement for food aid during emergencies, so a decent baseline). For typical rations, this is about 590 grams of food per day (not per year!), or about 1.3 pounds.

Given our math earlier, the Imperial Providence could probably carry a mix of foodstuffs from the Agriworld - we’ll call it a 80/15/5% split between grains, protein, and basic nutrients/fats. That works out to ~57mm3 grains, ~10.5mm3 protein, and ~3.5mm3 nutrients/fats.

The grains are fairly straightforward. Wheat weighs about 60lb per bushel (decent estimate for grains), so that’s 96 billion pounds of grain (someone else can convert that to megatonnes!). That would feed 200 million citizens

Oddly, 1 m3 can hold about 500 chicken breasts (0.5lb each, if we’re back to the WHO measurement). So the Imperial Providence would be carrying about 5.25billion chicken breasts (factory farms!). That would feed about 5 million citizens.

I have no idea how to quickly calculate the weight/scale of generic fats and sugars, so we’ll just say that the ship is carrying enough for another 5 million citizens and that the rest of the space is full of various other spices and additives that the population enjoys.

So, a governor that doesn’t completely hate his people could import enough food for ~210 million citizens on each load.

Those numbers are for a completely balanced diet, with enough calories to work as hard as necessary at whatever grimdark job the citizen has been tasked with.

If we assume that a major hive world can unload a single transport every week, which seems like a fairly conservative guess, then a hive world could easily keep 11 billion citizens fed.

The question of where all the waste products go is a question for another post

Keep in mind that what we're trying to work out here is spoilage that would occur given modern (or better) preservatives and refrigeration technology but requiring an age of sail time to go from farmers field to the mouths of citizens.

A quick google search turned up a study from the FAO (the U.N. group). In the industrialized world, only about 10% of cereals are lost or wasted during production, initial processing, and initial distribution. It looks like the rest is lost on the plate (which would be calculated into the consumption numbers of Americans that I quoted above).

So it doesn't look like the ships would need much extra space at all, especially if we were only counting the losses during distribution (less than 5% with modern refrigeration and techniques)..

Keep in mind that what we're trying to work out here is spoilage that would occur given modern (or better) preservatives and refrigeration technology but requiring an age of sail time to go from farmers field to the mouths of citizens.

A quick google search turned up a study from the FAO (the U.N. group). In the industrialized world, only about 10% of cereals are lost or wasted during production, initial processing, and initial distribution. It looks like the rest is lost on the plate (which would be calculated into the consumption numbers of Americans that I quoted above).

So it doesn't look like the ships would need much extra space at all, especially if we were only counting the losses during distribution (less than 5% with modern refrigeration and techniques)..

Right but we transport goods much faster on earth than the Imperium would be able to between planets. The UN numbrs are great and it gives us a frame work to use but how much food goes bad during transport would most likely follow an exponential curve, most things in biology do.

We need numbers specific to modern spoilage as a result of transport and duration of said transport.

But from what RamiVandigrath is saying it i still going to be feasible.

Whats everyone's opinion? Unhindered Growth policy (which requires the discovery of new agr-worlds at least every few 1000 years or so) or the Sustainable policy.

Personally with the new figures I think Unhindered Growth is the more likely of the two, and very fitting of the Imperium.

Enough said

Considering the whole "One million planets" thing of the Imperium. How about translating it to "One milion sectors ?" Then, it would be more at a galactic scale, allow to loose planets on roundings errors just as according to the fluff ...

In the beginning of almost every Black Library novel:

"He is the master of Mankind by the will of the gods, and the master of a million worlds..."

The whole quote has been around since the earliest days of Warhammer 40,000: Rogue Trader.

I mean, it's not like this RPG is a sci-fi game or anything? So there must be some justification to it's rules, right?....... :huh: No? <_< .......

Considering the whole "One million planets" thing of the Imperium. How about translating it to "One milion sectors ?" Then, it would be more at a galactic scale, allow to loose planets on roundings errors just as according to the fluff ...

On the old Black Industries forums, I once asked someone far more mathematically inclined than myself to work out how many 200 light year x 200 light year cubes you could actually fit into a frisbee-shaped Milky Way galaxy roughly 100 000 light years across. He reckoned 300,000. So (if he was right) you couldn't fit 1 million sectors into the galaxy. And that calculation assumes sectors stack like cartons of cereal in a packing crate: as you can see from the map in DH1, this assumption is incorrect. Sectors float freely at random angles to local neighbouring sectors, with a lot of wilderness space between them.

So 1,000,000 sectors seems way out to me. Plus, 1,000,000 sectors means 250,000,000 Imperial worlds, meaning a quarter of a million worlds for each space marine. I mean I know they're tough, but they're not THAT tough!

I prefer my 4,000-5,000 sector estimate...

On the old Black Industries forums, I once asked someone far more mathematically inclined than myself to work out how many 200 light year x 200 light year cubes you could actually fit into a frisbee-shaped Milky Way galaxy roughly 100 000 light years across. He reckoned 300,000. So (if he was right) you couldn't fit 1 million sectors into the galaxy. And that calculation assumes sectors stack like cartons of cereal in a packing crate: as you can see from the map in DH1, this assumption is incorrect. Sectors float freely at random angles to local neighbouring sectors, with a lot of wilderness space between them.

There once was a Topic in this forum on that very same subject, with a lot of calculations involved. And basically... well, you just summed it up, actually. :D

I prefer my 4,000-5,000 sector estimate...

I agree. The "master of a million worlds" is, IMO, just a ballpark figure FFG, or fantasy authors writing for FFG, has utilized for us to grasp how big the Imperium is. As you and previous posters pointed out, mathematically it could be higher, but other factors are present (diseases/germs, exterminates :blink: , other xeno species, worlds not discovered/lost :o ) which means it definitely is not less then 1 mil, but probably more though no one truly knows.

Yeah, I actually agree with you (more or less) in terms of gross availability of hulls and crews (although I suspect there are far more hulls than there are officers and specialists to crew them, given the existence of the Reserve fleets). I was more quibbling over terminology. I guess it's like the arbites being used as a generic term for law enforcement, despite the fact that most of the organisations and persons so described are not members of the Adeptus Arbites. With that in mind (and while there is some extrapolation from canon - Passage Watch 27-Est for example - I must admit this is guesswork), a Battlefleet is not technically a Battlefleet unless set up to combat a specific threat, but any formation of warships may be colloquially referred to as a battlefleet, even if they technically have their own permanent designation.

I forgot about the reserve fleets! My thinking on reserve fleets is that they don't so much consist of ships that the Navy doesn't have crew for, (but that's a possibility) but to a greater degree consist of ships that are not economic or safe to operate except in cases of dire emergency. A lot of the Mid M35 "chaos cruiser" and grand cruiser patterns are heavily implied in a number of sources to be inherently flawed designs that tend to warp and corrupt their crews, and as such are not well regarded. Grand cruisers are only slightly more powerful than battlecruisers, but require disproportionately large crews to operate. Plus, reserve fleets in space don't operate like reserve fleets in the modern, planet bound world: spaceraft don't decay in a vacuum. They don't rust or fall apart. Kept in deep space reserve yards, they are effectively immortal. So it's probably more trouble to attempt to dismantle a ship than it is to just leave it sealed up in a naval yard for centuries.

er...so where was I going with this again? Sorry, got carried away... Ah yes. Ship numbers. I'd completely forgotten about reserve fleets. What do you think represents a reasonable size for a Sector reserve fleet? 10% of the size of the rest of the "active" fleet? 20%? Somewhere between those two sounds about right... so in the case of a 200 strong Sector Fleet, this would mean 20-40 mothballed ships of various classes, probably with a higher percentage of capital ships than the fleet proper... Any thoughts?

There will be escort squadrons too; albeit ecclectic ones. This will be the source of a lot of the frigates and destroyers operated by rogue traders - " c'mon, you're not using it, are you ?" - and will get topped up in that any ship the Navy buys in as a prize from its frigate captains (which would mostly be raiders operated previously by pirates), that can be mobilized as an expendable reserve in time of war.

But yes, about 1/4 again as a stood-down reserve sounds fine.

Equally, of the 'active fleet', you can probably work on 1/4 of the fleet stood down for resupply, refit and maintenance at any one time

Cool. So to summarise:-

  • Roughly 1,000,000 inhabited human worlds in the Imperium, precise number unquantifiable
  • The Imperium is divided into 4,000-5,000 Sectors, precise number probably also unquantifiable
  • Sectors have on average roughly 200-250 worlds, though this will vary tremendously
  • The Imperium probably tries to operate a 1:1 Imperial Navy ship:Inhabited world ratio, with an additional 10-25% of this total additionally kept in reserve fleets. This will also vary tremendously.
  • Each Sector operates a merchant fleet that is probably 2000-2500 strong, though again this will vary tremendously.

I mean, I know I've plucked these numbers largely from the air, without real canon sources, but it's gratifying that the majority of people agree that they feel about right. This doesn't mean that GW won't change things so these numbers become incorrect in the future, though.

One thing on Sectors that just occurred to me is the existence of "mini sectors". I seem to recall that the Badab War books described at one point an area of space where the Mantis Warriors recruited their neophytes. I don't have the book to hand, but I think I remember that this was a grouping of a few dozen worlds that was too small to be a Sector proper, and too distant to attach to another Sector as a Subsector, but which did consist of loyal Imperial worlds.

Mulling this over, I guess logically there might be quite a few of these "mini sectors"; consisting of groups of worlds too small to amount to a sector proper, and too remote geographically to add to an existing sector. Given that there's only one example of these from the canon, it's hard to guess how many Imperial worlds fall into this nebulous middle ground category, but one imagines that if the "1,000,000 worlds" is a relatively fixed point of reference, the existence of "mini sectors" would serve to drive down the total number of "normal" sectors. However, it's hard to tell by how much.

EDIT: one point that's concerning me is that if I'm right about the 1:1 Imperial Navy ship:Imperial planet ratio, this means that there's about 1,000,000 Imperial navy ships. Does this figure feel right to people? It didn't sound too bad to me at first, but then I just thought "Hold on, that means one Imperial Navy ship for each space marine." It also means that (assuming an average marine crew complement of 50-250 per Astartes ship) Imperial Navy ships outnumber Space Marine craft about 50-250 to 1. Is that about right in your view? I'm unsure if that means my figures are wonky or not... :wacko:

Edited by Lightbringer

I remember reading somewhere there are about 1,000 SM Chapters (give or take a few dozen that die off and/or have been replaced every so often). So, with 1,000 SMs allowed per Chapter you get roughly 1 mil SMs. Obviously, this does not include serfs, neophytes, Tech-priests, servitors, slaves, inductees, men-at-arms, tag-a-longs, etc., residing in the Chapters.

Anyhoot, yep, your summary sounds about right.... I mean, I concur with your assessment. :)

And it goes without saying (though I'm going to say it for those who skipped to the end here) the 1 mil Navy ships don't include Admech Ships, RT privately owned vessels, PDF Fleets, etc. etc.

Cool. So to summarise:-

  • Roughly 1,000,000 inhabited human worlds in the Imperium, precise number unquantifiable
  • The Imperium is divided into 4,000-5,000 Sectors, precise number probably also unquantifiable
  • Sectors have on average roughly 200-250 worlds, though this will vary tremendously
  • The Imperium probably tries to operate a 1:1 Imperial Navy ship:Inhabited world ratio, with an additional 10-25% of this total additionally kept in reserve fleets. This will also vary tremendously.
  • Each Sector operates a merchant fleet that is probably 2000-2500 strong, though again this will vary tremendously.

I mean, I know I've plucked these numbers largely from the air, without real canon sources, but it's gratifying that the majority of people agree that they feel about right. This doesn't mean that GW won't change things so these numbers become incorrect in the future, though.

One thing on Sectors that just occurred to me is the existence of "mini sectors". I seem to recall that the Badab War books described at one point an area of space where the Mantis Warriors recruited their neophytes. I don't have the book to hand, but I think I remember that this was a grouping of a few dozen worlds that was too small to be a Sector proper, and too distant to attach to another Sector as a Subsector, but which did consist of loyal Imperial worlds.

Mulling this over, I guess logically there might be quite a few of these "mini sectors"; consisting of groups of worlds too small to amount to a sector proper, and too remote geographically to add to an existing sector. Given that there's only one example of these from the canon, it's hard to guess how many Imperial worlds fall into this nebulous middle ground category, but one imagines that if the "1,000,000 worlds" is a relatively fixed point of reference, the existence of "mini sectors" would serve to drive down the total number of "normal" sectors. However, it's hard to tell by how much.

EDIT: one point that's concerning me is that if I'm right about the 1:1 Imperial Navy ship:Imperial planet ratio, this means that there's about 1,000,000 Imperial navy ships. Does this figure feel right to people? It didn't sound too bad to me at first, but then I just thought "Hold on, that means one Imperial Navy ship for each space marine." It also means that (assuming an average marine crew complement of 50-250 per Astartes ship) Imperial Navy ships outnumber Space Marine craft about 50-250 to 1. Is that about right in your view? I'm unsure if that means my figures are wonky or not... :wacko:

There are regions which don't qualify as a sector (as you say, the Maelstrom is a good example), or are otherwise exempted from normal sector constraints. Ultramar is another good example.

However, there are also inter-sector worlds, which are perfectly loyal imperial worlds in the arse end of nowhere. Damaris in Rogue Trader is a perfect example; there are no other "proper" imperial worlds nearby it might form a 'sector' or 'subsector' with; so it's theoretically an imperial world, and would be registered as such with the Segmentum authority, but have no intervening lord sector to report to. References to worlds which see imperial traffic once in X centuries or whatever (adn there are plenty in the stories) are probably like this; if they were part of a sector with reasonable interstellar traffic they'd see reasonably regular patrols even if the world itself is fairly primitive, if only to make the point that the navy and lord sector is watching. Inter-sector worlds, however, might be several years warp travel from the nearest navy base that gives a **** about their existance....

To sum up a milion worlds Imperium is imho just a rhetorical figure just like a thousend year reich.

You know, that's kind of how I've always seen it, too! A rhetorical boast about the size of the Imperium, with no real idea as to the actual number.

As an aside, is anyone able to provide canon sources on the "Imperium of a million worlds" phrase and where this concept first appeared?

I don't have the page number handy, but I know it goes back to at least the 3rd ed. Warhammer 40k minis rules. It might go back even further.

You need to consider more than just grain in food transportation. Through most of human history grain accounted for 90% of bulk cargo, but that changed drastically in the 20th century with the advent of tankers, then container ships. Someone already pointed out the problem with spoilage, hence the reason why grain had always dominated the bulk carrier market. Grain might spoil, but at a far lesser rate than other foods.

Those people on Scintilla demanding better food rations are going to need a nice refrigerator ship to bring them fresh produce, and that ship is going to have to be on a dedicated run because refrigeration has its limits, too. I guess that brings up the notion of a cryogenic agriculture industry.

I'm seeing transport ships with container sections, tankage, bulk grain storage, cryogenics storage, cold storage, wet storage, and myriads other cargo-carrying capacity, since as it was pointed out, a single transport could carry enough wheat to feed 600 million people.

Ores are not going to be carried. It really drives me crazy to see that in some fluff. Bulk-reducing industries, such as metals, are going to have smelters, and probably foundaries, on the spot to reduce the bulk. Ingots and such would be shipped instead, or cold rolled and drop forged sheets of immense size.

I'm sorry I missed this thread earlier this year. I love talking logistics.

I agree that the numbers are (literally) astronomical, Austin. This is why I think that a 1,000,000 world Imperium seems a little small to me. But this 1 million number does seem to crop up again and again.

I like Erathia's point about the apparent relative dearth of inhabitable worlds in the Imperium possibly being due to the Fall of the Eldar and the Horus Heresy. That has to be true. Plus many of the Great Crusade era Legions (Death Guard especially) seem to have been quite trigger happy when it came to using exterminatus class weaponry.

Maybe its the number of habitale worlds with enviroments similar to earth, and the rest is made up of gas giant mining colonies, dead worlds, death worlds, planets without atmosphere where people live in domed outposts... Stuff like that.

As a possible counter to spoilage, what about cyro-storage? Or stasis chambers?

Lightbrighter, your values do indeed "feel" right, or at least not so far off. Losing a sector would be a sad thing, but if it isn't even one tenth of one percent of your total holdings it is hardly a crippling loss.

One thing I've always considered with the Imperium and the "1,000,000 Worlds" statement is that they're only referencing those worlds that are actual colonies of significance (even if they're only feral or feudal worlds).

That is to say, every lonely research station, outpost, or mining camp, isn't counted among the figure.

It still leaves a lot of untouched worlds in the galaxy, but it's one more way to eat up some of that space (not to mention the Eye of Terror, Maelstrom, and the ragged edges of the galaxy).

I think 1 million stellar systems feels about right. That's 1 million systems with 1 decently habitable planet and numerous stations, colonies, outposts, installations, etc.