Converting D&D modules to GURPS (quickly)

[sjmdw45]

Someone asked me in a PM about how I convert D&D Dungeon Crawl modules to GURPS, and perhaps I should also post my guidelines here. My main goal is to be able to run GURPS adventures straight out of the D&D booklet--I may convert some monsters in advance for convenience but I should be able to do it in my head if necessary.

For required skill rolls, DC 15 is an unpenalized roll vs. a relevant attribute/skill in GURPS. Every +2 to DC is a -1 penalty in GURPS. Note that this means a GURPS character with Per 10 operating off of a Traps default (from memory, I think that's a -5 default) has 50% odds of detecting a DC 5 trap. In practice, many PCs will have Per higher than 10 and/or points in Traps so I think this is okay. Sometimes D&D modules give extra information about monsters on high DC rolls, and the same guidelines apply here: every 10 extra DC is 5 points on GURPS rolls. Obviously there will be some cases where the D&D rules just don't fit--where it's obvious that they're trying to shoehorn something into the D&D ruleset that would be more naturally done in GURPS--and in this case I ignore the D&D stats.

For the monsters, my basic rules of thumb so far have been:

1. Take basic stats St/Dx/Con/etc. ST = St. DX = 5+Dx/2. IQ = 5+Int/2. Will = 5+Wis/2. Per also = 5+Wis/2. HT = 5+Con/2. Cha I haven't done anything with so far but it would be on the order of +1 reaction bonus per +2 Cha over 10, or vice versa if Cha is under 10.

2. For each 1 HD of the monster, it gets either 1.) +1 to ST, 2.) +2 to HP (note that +1 to ST includes +1 to HP so this is really only trading 1 ST for 1 HP), or 3.) 4 points in a combat skill.

3. For every 5 HD, it gets either 1.) +1 to DR, 2.) +1 HT, or 3.) +2 ST.

4. DR = (flat-footed AC - 10) / 2. If touch AC is better than 10, give 1 level of Enhanced Parry, Dodge, or Block per 2 points of AC (depending on the monster which it will take), or else it can buy Combat Reflexes for 3 points of AC.

5. Skills (non-combat), again, get +1 in GURPS per +2 in D&D. I suppose I should subtract out the D&D ability bonuses first to figure out how many "real" plusses the monsters have in stats, but so far I haven't.

The important thing to me is not exactly fidelity to the exact toughness level of the D&D monster. Some monsters will be relatively weaker in GURPS stats and some (like orcs) will be relatively stronger. What I want is 1.) a consistent methodology that lets me pretty much convert monsters straight across without a lot of tweaking, where I could read the GURPS stats right off the D&D page if necessary, and 2.) some verisimilitude (the right "feel") for monsters in GURPS, using the D&D stats as a guide. So a Tyrannosaur in D&D is a 20 HD beast? Okay, in GURPS it's a ST 45 beast with HT 12 and DR 1. And I'll eyeball it and add Fangs and Sharp Claws--note that I'm otherwise ignoring the listed D&D damage of attacks, since I'll compute that from its ST.

Edit: Oh yeah, and 1 gp is worth $10 in GURPS. Although gp/sp are the standard currency. I don't have clear guidelines for converting magic items. Also, corrected a mistake above.

And also, 5' of D&D Move = 1.00 GURPS Basic Move. Basic Speed is computed from HT/DX normally.

I hope that's useful.

-Max

P.S. Note that I'm trampling all over point values here. 1 ST is not equivalent to 2 HP in GURPS point terms, but I don't care.

[Kaldrin]

Or even faster yet. Ignore the D&D mechanics and use your own stats for foes and situations that make sense. As long as you're consistent you should be able to do it on the fly without too much getting in the way. Also, you aren't bound do the numbers and can make something more difficult or easier in the favour of higher theatrics for the situation.

[Ed the Coastie]

Sounds good...except for the fact that I use little to no D&D 3e material in my games. D&D for me is often referred to as OD&D, which I use extensively in conjunction with a lot of AD&D (1e) and AD&D 2e material.

[Fred Brackin]

Originally Posted by sjmdw45

[COLOR=Red]Edit: Oh yeah, and 1 gp is worth $10 in GURPS. Although gp/sp are the standard currency. I don't have clear guidelines for converting magic items.

My World of D'y'r't campaign runs on 1 gp equals $10. Magic items are Gurps standard (or unique conversions for found items) bought for 5 GP per pt of energy. Excessively complicated items and artifacts are sold for the old system book value given.

That's essentially the same S&S rate as 3rd edition (which makes the old Magic Item books more usable). The official 4e rate would be 6.6 GP but that's too finicky and I prefer the round numbers.

I do sell some very small items for the Q&D rate. Potions are the Alchemical equivalent.

The usual assumption for enchanting appears to be some sort of plutomancy where GP are turned into energy pts on a short term basis. Except for the group's cleric. He gives appropriately sized offerrings and gets his items drop-shipped from the Realm of the Gods.

Like Ed the Coastie I am seldom working with D&D 3.x. Usually it's Hackmaster. I bought a lot of those at fire sale prices. They actually convert more easily than 3.5.

[sjmdw45]

Originally Posted by Ed the Coastie

Sounds good...except for the fact that I use little to no D&D 3e material in my games. D&D for me is often referred to as OD&D, which I use extensively in conjunction with a lot of AD&D (1e) and AD&D 2e material.

Sure. I've played AD&D2, and still own a certain amount of Spelljammer material, and in fact I've never played D&D3 at all. However, the modules I'm running at the moment happen to be written in 3e. I would use basically the same approach for converting old AD&D2 material because the key factor--d20 vs. 3d6--remains the same.

@Kaldrin. More power to you.

-Max

[Rasputin]

Originally Posted by sjmdw45

Oh yeah, and 1 gp is worth $10 in GURPS. Although gp/sp are the standard currency.

One $1 is 2 cp in D&D 3e. Since a GURPS $1 is defined as the cost of bread or other staple, and such costs 2 cp in D&D, this is the conversion. This means that 1 gp = $50 GURPS (using the decimalized 100 cp = 10 sp = 1 gp). And if you use that conversion of the PHB, you'll find that the weapons and armor therein do have similar costs to their equivalents in the Basic Set.

Originally Posted by sjdm45

And also, 5' of D&D Move = 1.00 GURPS Basic Move. Basic Speed is computed from HT/DX normally.

For the most part, you're best off using default values calculated from Basic Speed. D&D movement rates map alright to GURPS -- not exact, but you're not off enough to care. (Calculation = a character with Speed 30 ft. in D&D can run 120 ft., or 40 yd. Converting from 6 second to one second combat rounds and subtracting the +1 sprinting bonus, you have a Move 5.67, which is a smidgen better than normal. Your dwarves with Speed 20 ft. in D&D come out to Move 3.44 in GURPS, a bit low.)

Some other scribble-in-the-margins calculations:

* Try skill ranks as character points in that skill. It keeps some of those skills from going too high at high levels.
* For AC, set DR to half of the natural armor bonus. Don't translate the armor and shield bonuses; use the values of the equivalent armor in the Basic Set.
* I keep wondering what the best way to translate Strength is. Let's see ... a Str 10 D&D character can carry 100 lb. if he's Medium size. A ST 10 GURPS character has Basic Lift 20 lb. and Extra-Heavy Encumberance at 200 lb. So take the square root of the D&D carrying capacity for GURPS ST. Personally, I would use Str/2=5 = ST for humanoid creatures, since it translates the damage, which is about what we really care (each single-point increase in ST increases the swing damage by about a point). For the T.Rex, translating carrying capacity, it can carry 4,800 lb. (it has Str 28, giving it a carrying capacity of 1,200 lb., which is quadrupled for being Huge), so its GURPS ST is 70 (the computer I'm using right now has calc.exe locked down, so I can't be exact) by this method ... too high, methinks. Average that with the ST 19 we would have by Str/2+5, I guess.

[sjmdw45]

Rasputin,

Thanks. I'll have to modify your procedures for computing ST, though, because I don't own any D&D3 books so I don't know carrying capacities. Good ideas.

-Max

P.S. I always use Google as my calc.exe. Type in sqrt(4800) and it responds, "sqrt(4 800) = 69.2820323". Neat.

[Rupert]

Originally Posted by sjmdw45

Edit: Oh yeah, and 1 gp is worth $10 in GURPS. Although gp/sp are the standard currency. I don't have clear guidelines for converting magic items. Also, corrected a mistake above.

That makes swords really cheap, at $100 for a shortsword, and $150 for a longsword. OTOH, given the amount of loot D&D modules traditionally hand out, I suppose you need a weak D&D GP.

[Rupert]

Originally Posted by Rasputin

For the most part, you're best off using default values calculated from Basic Speed. D&D movement rates map alright to GURPS -- not exact, but you're not off enough to care. (Calculation = a character with Speed 30 ft. in D&D can run 120 ft., or 40 yd. Converting from 6 second to one second combat rounds and subtracting the +1 sprinting bonus, you have a Move 5.67, which is a smidgen better than normal. Your dwarves with Speed 20 ft. in D&D come out to Move 3.44 in GURPS, a bit low.)

That's why I use D&D move / 10 + 2 = GURPS Move.

* I keep wondering what the best way to translate Strength is. Let's see ... a Str 10 D&D character can carry 100 lb. if he's Medium size. A ST 10 GURPS character has Basic Lift 20 lb. and Extra-Heavy Encumberance at 200 lb. So take the square root of the D&D carrying capacity for GURPS ST. Personally, I would use Str/2=5 = ST for humanoid creatures, since it translates the damage, which is about what we really care (each single-point increase in ST increases the swing damage by about a point).

It doesn't quite work that way, because of GURPS having swing and thrust damage, and D&D giving extra damage for two-handed use. I've found Str - 2 = GURPS ST works adequately. By carrying capacity it's closer to Str = ST over the human range.

For the T.Rex, translating carrying capacity, it can carry 4,800 lb. (it has Str 28, giving it a carrying capacity of 1,200 lb., which is quadrupled for being Huge), so its GURPS ST is 70 (the computer I'm using right now has calc.exe locked down, so I can't be exact) by this method ... too high, methinks. Average that with the ST 19 we would have by Str/2+5, I guess.

By its weight a T. Rex in GURPS would be expected to have ~ST50. Assuming a reasonable Brawling skill it would do 5d+6 cutting with its bite.

[robertsconley]

I found that 20 to 50 pts per HD or Level works pretty good. I use the D20 stats to figure out how the final stats should approportioned along with skills and advantages (and disadvantages).