Success Roll

A success roll is fundamentally a roll of 3d6, adding them up, and trying to roll equal to or less than some target number; various other rules may modify this roll. The target number is usually equal to effective skill rather than actual skill via bonuses and penalties from Task Difficulty Modifiers and Size, Speed, and range. Success Rolls involving attributes are handled much the same way.
==Crit Rules==
"Any roll of 10 greater than your effective skill is a critical failure"Basic Set, p.348
==Probability Table==
Because GURPS uses a bell curve it helps to understand the chances to get a certain roll. The percentages are rounded with the total number of outcomes being 216. The rough d20 equivalents (based on percentage) are provided to help with any D&D to GURPS conversion.
 	3-4	5 	6 	7 	8 	9 	10 	11 	12 	13 	14 	15 	16 	17 	18
Number of combinations	4 	6 	10 	15 	21 	25 	27 	27 	25 	21 	15 	10 	6 	3 	1
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
d20 	20 	20 	19 	17 	15 	12 	10 	8 	5 	3 	2 	2 	1 	1 	1
==Critical Success and Failure Tables==
Wildcard skills have an option for extending the range for Critical Success. The Cinematic Extended Critical Table in GURPS Compendium II p. 73 provided an extension for mundane skills. 
Normal Critical Table
Modified Skill 	2 orless	3 	4 	5 	6 	7-14 	15 	16+
3d6 Critical Success	NR* 	3-4 	3-4 	3-4 	3-4 	3-4 	3-5 	3-6
d20 Critical Success	NR* 	20 	20 	20 	20 	20 	20 	19-20
Critical Failure 	NR* 	13-18	14-18	15-18	16-18	17-18	17-18	18
d20 Critical Failure	NR* 	1-4 	1-3 	1-2 	1 	1 	1 	1
* 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. This works out to be 8 and 5 respectively on a d20.
Cinematic Extended Critical Success Table
3d6 Critical Success 	3-7 	3-8 	3-9 	3-10 	3-11 	3-12 	3-13 	3-14 	3-15 	3-16
d20 Critical Success 	18-20 	15-20 	13-20 	10-20 	7-20 	5-20 	3-20 	2-20 	2-20 	2-20
Compendium IISkill Level 	20-24 	25-29 	30-34 	35+ 	NA 	NA 	NA 	NA 	NA 	NA
WildcardOpen-EndedSkill Level 	17 	18 	19 	20 	21 	22 	23 	24 	25 	26
WildcardSlow Open-EndedSkill Level 	18-19 	20-21 	22-23 	24-25 	26-27 	28-29 	30-31 	32-33 	34-35 	36-37
WildcardRelatively CriticalHalf-BonusSkill Level	Att+360 pt	Att+372 pt	Att+484 pt	Att+496 pt	Att+5108 pt	Att+5120 pt	Att+6132 pt	Att+6144 pt	Att+7156 pt 	Att+7168 pt
WildcardRelatively CriticalBonusSkill Level 	Att+248 pt	Att+360 pt	Att+472 pt	Att+584 pt	Att+696 pt 	Att+7108 pt	Att+8120 pt	Att+9132 pt	Att+10144 pt	Att+11156 pt
==Additional Details==
*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
==Special Cases==
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
==Crits and Magic==
http://forums.sjgames.com/showpost.php?p=2452818&postcount=21 alleged Kromm post
The intent behind very high mana is that any personal FP spent on magic regenerates one second after being spent. Whether "spent on magic" means "cast," "maintain," "contribute," or some other thing is merely arguing over semantics, being a rules lawyer.
The intent behind critical success is completely different. It's a link between the roll to cast and the results of casting, so it's quite clearly applicable only to the energy you had riding on the dice roll to cast, and thus to casting. On the other hand, it's all energy and not just personal FP . . . and it's a case of "never spent in the first place," not regeneration.
The two cases aren't meant to be symmetric or related in any way. About all they have in common is that a caster ends up with more FP kicking around.
==Ordinary Working Professionals==
"The standard rules are designed for adventurers, not for ordinary working professionals. Professionals make one job roll a month. On a critical failure, something bad happens, with harmful consequences – but not usually as bad as a critical failure during an adventure. (...)With one roll a month, a mage with effective skill 15 or less goes 54 months between mishaps, on the average; one with effective skill 16 or better could go 216 months (or 18 years)."Thaumatology: Urban Magics, p.30
==References==
*Basic Set, p.345-6
Category:Rules