I prefer FFG's narrative dice to standard d20, but I have friends who prefer d20 so I thought it would be fun to try to convert it (with a couple additions/subtractions) to d20.
In truth, it is not so much a conversion as a system made to be compatible.

There are a couple things I changed. I actually removed Cunning, nesting it under Intellect, and I changed how some of the skills are handled. Some of the skills I split into 3 smaller skills (such as Mechanics: Droids, Devices, and Vehicles). One other point on Skills, no personally wielded weapons use Gunnery (i.e. Cip-Quad, HRB, etc.) they use the new "Heavy Weapons" Skill (nested under Ranged (Heavy). Only vehicle mounted, remote controlled, etc. weapons use Gunnery.

Starting species XP is doubled.

I took a lot of inspiration from GURPs (thanks @Mark Caliber ) for some of the mechanics. I'm considering adding "Advantages" like are in GURPs, but I haven't gotten there yet (and am not entirely sure that I will.

The basic dice mechanic: In order to maintain the narrative effects, you roll 2 separate dice; 1 d20 and 1 d12. The d20 is your success/failure die, and the d12 is your Advantage Threat die. The d20 is binary. If you fail, you failed, if you succeed (and multiple success would mean something) you roll a second die to determine how much Success you garnered. The 12 is not. For every 2 points above/below the difficulty, you get 1 Advantage/Threat, to be spent like Advantage and Threat in FFG's system.

As far as stats for weapons and gear go, I intend them to carry over. I don't think that there is anything I messed up, but there might be. For stuff that adds X Advantage or X Success, you simply add 2 Advantage points (the raw resource generated by the d12, before you divide by 2) per. For Success, you add 3 to the d20 result (per) and if you succeed by more than you added, you add 1 Success (per) to the result of the second die.

Before any objections pertaining to "but there's too much math" you can just write down your calculated D+ next to each skill for quick reference (your calculated D+ is the D+ from Characteristic+ the D+ from Skill. There is no need to calculate Secondary Characteristics into the equation as they don't always apply).

I would greatly appreciate any game breaking, testing, and feedback you can provide, as this is very much a work in progress.
Rules: https://docs.google.com/document/d/1a1EbedPiElsC1RKaTj2LyzAMGp4QsGygHOj6vgRLH7I/edit?usp=sharing
Character Sheet: https://docs.google.com/document/d/1OIDLwJVPDTZ2UDq9q9-ofVfQQEMKSaefb16-YCFjpAQ/edit?usp=sharing

Human species stats: 4 Str, 4 Dex, 4 Int, 4 Will, 4 Char. WT 10+Str, ST 10+Will, 220 starting XP. Same special ability as RAW.

Given there's already a couple different versions of d20 Star Wars out there, as well as at least a couple different homebrews using 5e D&D as the baseline that can be obtained for free (at most you'd need a copy of the Basic Rules document, which can be freely obtained from WotC's website), I'm wondering just what you're trying to accomplish here beyond a lot of self-induced frustration and aggravation.

This system and d20 are to very conceptually opposed systems, so trying to map one to the other is going to present a large number of hurdles and obstacles, especially if you're involving GURPS (a notoriously crunch-heavy system) as part of the conversion process.

Have you actually looked at the doc?

My goal is to retain the spirit of this system, but switch it over to using regular dice (and less of them) as well as changing certain things (plus, frustration/aggravation is hard for me to attain doing something like this. This is something I enjoy).

As far as GURPs goes, I'm not copying the system or using it for the conversion, I'm just taking inspiration for certain elements (like first impression rolls) from it.

I get the joy of rule-crafting (which should be obvious from everything I wrote below... ) , so don't let anything I say dissuade you...

Reading through the doc (not in great detail, I admit...there's a lot there), it seems like you've changed *all* the base lines, which is going to make converting and balancing much more difficult. You're not so much converting FFG to D20, you're inventing an entirely new system, and borrowing some labels.

It seems to me you could save a lot of headache by leaving the core characteristics etc alone, and concentrate on the odds, so you can switch to a D20 without losing too much. Somewhere out there on the interwebs are tables of stats created when the game first came out, but they basically boil down to: if you're rolling positive dice equal to negative dice, you have about a 45% chance of success. This is because you need +1 net success. (If you only needed net 0 or more, then the odds would be about 50-55%.) Each die extra either way adds/subtracts about 10%...which is a very rough number, because things start to vary wildly the more dice you add to the pool and the greater the difference between the positive and negative pools. But still, for the purposes of conversion you could stick with 10%, which is equal to +/- 2 on a D20.

This is just assuming base greens vs purples, and no upgrades. Adding upgrades doesn't change the chance of success by much, but it might be simplest to make it count as +/- 1 on the result. Same with boost dice and setback.

That's just the success/fail axis. For the narrative axis I wouldn't use a D12, I think 2d6 gives a more meaningful result because it generates a bell curve. You don't have to do any funky division because the bell curve takes care of it. Anything 8+ gives an Advantage per pip, eg: 8 = 1, 9 = 2, etc. Likewise, anything 6 or less is Threat, counted in the same way. Applying upgrades, boosts, or setback adds to or subtracts from the 2d6 result. So if the GM flips a DP to upgrade the difficulty, but the PC has two yellows and a boost in their pool, the net is +2 to the 2d6. It might be simplest to bundle the Despair/Triumph axis into this, then: a net result of 2 or less is Despair or 5T; and a net result of 12+ is Triumph or 5A. Getting a result higher than 12 or less than 2 just adds more Advantage/Threat. And maybe a natural 2 or 12 gives a Despair/Triumph no matter the final score.

For converting difficulties, in D20 an "easy" task is typically DC5, average is DC10, hard is DC15, etc. Most level 1 D&D PCs can do a Hard task 50% of the time, meaning they usually have +5 to add to the result. So in this conversion, if you had a PC Pilot that had to try a Hard task (3 dice), that would be a DC15 in the D20 system. If they had Agility 3, they get +6 to start. If they had 2 ranks in Piloting, add +2. If they're flying a YT-1300, the Handling gives -1, for a net of +7 on their D20, which translates to about a 60% chance of success. They'd also add +1 to the 2d6 roll (+2 from skill ranks, and -1 from Handling), which means on average they'd generate 1A.

The only thing you might have to tweak here is the DC increment, you might prefer increments of 4 (DC4, DC8, DC12, etc), or 6 (DC6, DC12, DC18, etc) or whatever.

One caveat: by separating the success dice from the narrative dice, it's going to generate a very different result pattern. The FFG system, given even dice pools, tends to generate success with threat, or failure with advantage...because dice that result in success aren't generating advantages to counter those with threat, etc.

...OR you could just play Saga. It's a pretty good system, despite it having all the flaws a D20-based game has.

1 hour ago, whafrog said:

You're not so much converting FFG to D20, you're inventing an entirely new system, and borrowing some labels.

That's actually what I set out to do, I just took enough inspiration and numbers (and gear, and talent trees, etc.) that I thought it wouldn't be right to try to call it my own.

1 hour ago, whafrog said:

One caveat: by separating the success dice from the narrative dice, it's going to generate a very different result pattern. The FFG system, given even dice pools, tends to generate success with threat, or failure with advantage...because dice that result in success aren't generating advantages to counter those with threat, etc.

Yeah, I know, and I'd thought about that, but I don't think there is a way around that, unfortunately.

1 hour ago, whafrog said:

That's just the success/fail axis. For the narrative axis I wouldn't use a D12, I think 2d6 gives a more meaningful result because it generates a bell curve. You don't have to do any funky division because the bell curve takes care of it. Anything 8+ gives an Advantage per pip, eg: 8 = 1, 9 = 2, etc. Likewise, anything 6 or less is Threat, counted in the same way. Applying upgrades, boosts, or setback adds to or subtracts from the 2d6 result. So if the GM flips a DP to upgrade the difficulty, but the PC has two yellows and a boost in their pool, the net is +2 to the 2d6. It might be simplest to bundle the Despair/Triumph axis into this, then: a net result of 2 or less is Despair or 5T; and a net result of 12+ is Triumph or 5A. Getting a result higher than 12 or less than 2 just adds more Advantage/Threat. And maybe a natural 2 or 12 gives a Despair/Triumph no matter the final score.

I'll try to cook up some numbers on this, calculating out the difficulty etc. but although the 2 d6 angle has its benefits, since I'm trying to stay as true as I can to the spirit of the narrative system, I don't want to put it on a bell curve because I'm not putting the success on a bell curve and it retains parity between Advantage/Threat and Success/Failure (and it makes it easier to calculate difficulty or convert the D+ modifiers).

One reason for the d12 (and this makes me a little sad cause you can't have a Triumph and a Despair on the same check) is that it gives the same odds of scoring a Triumph as rolling a single proficiency die and vice versa for Despair.

1 hour ago, whafrog said:

For converting difficulties, in D20 an "easy" task is typically DC5, average is DC10, hard is DC15, etc. Most level 1 D&D PCs can do a Hard task 50% of the time, meaning they usually have +5 to add to the result. So in this conversion, if you had a PC Pilot that had to try a Hard task (3 dice), that would be a DC15 in the D20 system. If they had Agility 3, they get +6 to start. If they had 2 ranks in Piloting, add +2. If they're flying a YT-1300, the Handling gives -1, for a net of +7 on their D20, which translates to about a 60% chance of success. They'd also add +1 to the 2d6 roll (+2 from skill ranks, and -1 from Handling), which means on average they'd generate 1A.

It's nice that my DCs actually line up with d20, that wasn't something I had intended (I don't actually play any d20).

Now, and this is something I'm thinking of changing, in the section on setting difficulty, I list "Upgrades" (disparate from skills) as 3/2 either to the difficulty or added onto the roll (depending on whether it was negative or positive) and I largely did that because it was the easiest to calculate, however, now I'm second guessing that and simply adding 1/1 to the difficulty, aside from the Despair adjustments (which is a section I just added to go with the Despair rules for Adversary). I'm going to change that for the positive upgrades as well. (this was a little stream of conscious)

As for Boost and Setback, 1/1 (Setback) and +1 to the D+ (Boost) were always the plan.
Skill ranks each add 1 to the D+.
Characteristics past 4 (the equivalent of 2) each add 1 to the D+, meaning that if you have the equivalent of 3 in a Characteristic, you add 2 to the D+, and that might be a tad low, but I think that it fits the best and if the difficulty gets a tad bit harder, than so be it. It isn't supposed to be a 1:1 ratio anyway. (I don't say this to try to brush you off on this point, I just think that if I were to change the numbers I might break it) *See below, I changed my mind*

In the example you gave, they would have a D+ of 3 (meaning 2 for the Advantage die), a difficulty of 16/10 (15/9 with 1/1 for the Setback), and that looks a little bit too hard. Hmm... I'm rethinking my above point, maybe instead of having it to where you can have a D- for a characteristic lower than 4, it should be a D+ equal to the Characteristic. I'll keep it as-is for now, and think it through. Maybe I will change that.

Remember, because of the different scale between the 2 dice, the D+ modifier is multiplied by .66 (another way to say that is 2 thirds of the D+) to get the number for the Advantage die.

Thank you for taking the time to write out your long and well thought-out critique, it really helped!

I really enjoy rule-crafting (hence 4-5 house rule threads with my name on 'em [most notably the tractor beam and atmospheric crashing ones]), and my goal with this was to try to have d20 without as much of the stuff I don't like as possible.

After thinking about it more, I have decided against changing the D+ from Characteristics because a character with the base human stats (flat 2s) would have a ~70% chance of succeeding at a check with Average difficulty (with a +4 from Characteristics, you would average a dirty 14), which is much too easy. Even though it makes Hard difficulty a little bit harder, I think that the way I have it is the best way to go about it (that I have come up with, at least).