With a total of 17 skills, each skill in Fallout: The Roleplaying Game starts at 0 and can advance up to 6 and no higher. Skills are used for skill checks and are paired additively with a SPECIAL attribute - each skill or attribute point is worth +5% and the normal range of possible values is 4-16, i.e. 20-80%. A number of d20s ordinarily equal to 2 plus any bought with Action Points are rolled, and the number of successes compared to the number the DM requested determines the outcome. For instance, the GM asks for a test against shooting a raider with Big Guns, difficulty of 1. The Big Guns default primary attribute is Endurance, and with 4 ranks of Big Guns and 8 Endurance that makes the target number for a success 12 (60%; average on 2d20 will be 1.2 successes, i.e. against a DC1 check, usually beating the check and generating 1/5 of an Action Point). Rolling 2d20, the results are 12 and 15. The 12 rolled under or equal to the target number and counts as a success, but the 15 rolled over and does not count for anything. 1 success was all that was needed to beat the raider's Defense, so the player hits in this instance. With 2 successes, the raider would be hit and the players would gain a single action point; with 2 failures, the raider would be missed.
Skill test summary[]
Add up your Attribute + Skill combination
Check the difficulty
(Optional) buy d20s using action points?
Roll the dice
Count your successes. Did you get enough compared to the difficulty?
Yes.
No.
Any extra successes become Action Points to spend or save.
The skill test was failed.
Determining skills[]
Three tag skills are available from during character creation, with each tag granting 2 ranks into the chosen skill. These chosen skills are important as these are the only skills that can achieve critical successes by rolling under the skill number. Standard Skill points are granted after the tagged skills starting at 9 + Intelligence.
The ability to communicate in a practical and efficient manner. The skill of convincing others that your position is correct. The ability to lie and not get caught.