Converting D&D DC to GURPS Skill penalties

sheakauffman · 01-14-2013, 05:57 PM

Sorry to Necro this thread, but I have actually worked out this problem.

First Average for d20 is 10, and average for Gurps is 0, since Gurps uses a "penalty shift" system.
And the average "default" penalty in Gurps is 5, which I think goes right in line with setting the base-case for Gurps at a DC 15. Which was arrived at by totally different means in the first post.

Now to get the mechanical conversion, you have to figure out the relative value of a +1, which you can figure by comparing the deviations from the means of the two systems. In the case of Gurps you have a deviation of 2.96, and in the case of d20 the deviation is 5.77. That means that you are close to a 2 to 1 value for each +1.

That means the following would more or less be equivalent penalties to DC's:

5 - +7
10 - +4
15 - 0
20 - -4
25 - -7
30 - -11
35 - -14
40 - -18

That being said, I can't remember seeing a penalty above 10 in Gurps. Gurps seems to max out at an (mechanical) equivalent of DC-30.

01-14-2013, 05:57 PM	#22
sheakauffman Join Date: Jan 2013	Re: Converting D&D DC to GURPS Skill penalties Sorry to Necro this thread, but I have actually worked out this problem. First Average for d20 is 10, and average for Gurps is 0, since Gurps uses a "penalty shift" system. And the average "default" penalty in Gurps is 5, which I think goes right in line with setting the base-case for Gurps at a DC 15. Which was arrived at by totally different means in the first post. Now to get the mechanical conversion, you have to figure out the relative value of a +1, which you can figure by comparing the deviations from the means of the two systems. In the case of Gurps you have a deviation of 2.96, and in the case of d20 the deviation is 5.77. That means that you are close to a 2 to 1 value for each +1. That means the following would more or less be equivalent penalties to DC's: 5 - +7 10 - +4 15 - 0 20 - -4 25 - -7 30 - -11 35 - -14 40 - -18 That being said, I can't remember seeing a penalty above 10 in Gurps. Gurps seems to max out at an (mechanical) equivalent of DC-30.