Thursday, December 9, 2021

Why a cap of Stat+10?

I've written before about setting caps on defenses, skills, etc. in GURPS.

A cap of Stat+10 as a limit dates back to 3rd edition. But why 10? Why not more, like 12 or 15, or less, like 4 or 6 like Talents?

On my drive home from a skill-training event*, I was thinking about the way GURPS has centered around +10:

-The TDM chart ranges from -10 to +10.

- the highest non-range penalties tend to cap at -10 (eyeslits of helms, chinks of armor over vitals, cannot see)

- stats tend to cap at +10 over base (humans range up to 20 in ST, DX, IQ, HT in most genres)

- Trying to do a long task "instantly" is -10.

There are few examples of very high penalties that aren't range, stacked penalties, or some combination of both.

So having a skill cap at Stat+10 is well in line with that. It has a symmetry - a true prodigy (DX or IQ 20) or a true master (Skill 20) can absorb the worst penalty and still have a 50/50 shot of success. A prodigy with mastery (DX or IQ 20 and stat+10 skill) still has mastery even faced with that penalty. That's not unreasonable as the true maximum.

I think that means Stat+10 makes sense as a potential cap.

* Aka, martial arts class.


  1. It's probably related to pentaphilia and the 3d6 dice range. Average+9 or -8 are unrollable so can in some ways stand in for infinity.

    1. Oh, that has to be true for the system overall. I wanted to just draw the lines between stat+10 and the other places +/- 10 have meaning.


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