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The Success roll is based on effective skill rather then actual skill.

Probability TableEdit

Because GURPS uses a bell curve it helps to understand the chances to get a certain roll.

3-4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Single % 1.9 2.8 4.6 6.9 9.7 11.6 12.5 12.5 11.6 9.7 6.9 4.6 2.8 1.4 0.5
Cumulative % 1.9 4.6 9.3 16.2 25.9 37.5 50.0 62.5 74.1 83.8 90.7 95.4 98.1 99.5 100

Critical Success and Failure TableEdit

Modified Skill Level Critical Success Critical Failure
2 or less NR* NR*
3 3-4 13-18
4 3-4 14-18
5 3-4 15-18
6 3-4 16-18
7-14 3-4 17-18
15 3-5 17-18
16+ 3-6 18

* If a non defense roll is attempted it is an automatic failure though the roll tells it is a normal or critical failure. For defense of 1 a critical failure is 11 and 2 is 12.

Extended Critical TableEdit

This was an extension of the above table given in GURPS Compendium II[1]

Modified Skill Level Critical Success Critical Failure
20-24 3-7 18
25-29 3-8 18
30-34 3-9 18
35+ 3-10 18

Additional DetailsEdit

  • a critical success on an attack roll is a Critical Hit
  • a critical success on an active defense results in a Critical Miss for the attacker
  • A critical failure on an attack is a Critical Miss
    • A successful attack is also a critical miss if an active defense critically succeeds to thwart it
    • A critical failure on a parry also functions like a critical miss
  • Other active defenses can also critically fail:
    • A critical failure on a block unreadies the shield
    • A critical failure on a dodge results in a fall

Task DifficultyEdit

Not all skill checks are created equal and difficulty modifiers are a way to simulate this.

  • Automatic: +10 or wave roll entirely
  • Trivial: +8 or +9
  • Very Easy: +7 or +6
  • Easy: +4 or +5
  • Very Favorable: +3 or +2
  • Favorable: +1
  • Average: no modifier
  • Unfavorable: -1
  • Very Unfavorable: -2 or -3
  • Hard: -4 or -5
  • Very Hard: -6 or -7
  • Dangerous: -8 or -9
  • Impossible: -10 or no success possible

Extra Time (noncombat actions): 2x as long gives +1, 4x gives +2, 8x gives +3, 15x gives +4, and 30x gives +5.
Haste: -1 per 10% less time taken; 90% (taking 1/10 the prescribed time) max.

Special CasesEdit

Per http://www.sjgames.com/gurps/faq/FAQ4-3.html#SS3.1.3 all rolls are impossible if target number is below 3, but are still rolled if attempter does not realize impossibility to determine if it is a normal failure or a critical failure. A roll of 3 can be a critical failure if rolling against a -7 skill.

Exceptions are:

  • defense rolls
  • resistance rolls to magic or poison
  • most forced IQ and HT rolls
  • any other resistance roll against a force directly targeting a living or sapient being

ReferencesEdit

  1. pg 73
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