Rollune
d20 systems (D&D, Pathfinder) roll one die plus modifiers against a target. Percentile systems (Call of Cthulhu, Warhammer) roll under a skill on d100. Dice-pool games (Blades in the Dark, Shadowrun, Vampire) roll many dice and count successes. PbtA games roll 2d6 for full, partial or failed results.
d20 systems
Dungeons & Dragons 5e: d20 + modifiers vs a target (AC or DC). Advantage rolls two d20s. Pathfinder 2e: d20 + modifiers, but beating the DC by 10 or more is a critical success, and missing by 10 a critical failure. A natural 20 or 1 shifts the result one step. Cypher System: d20 against a difficulty times 3.
Percentile (d100) systems
Call of Cthulhu 7e: roll equal to or under your skill on d100. Half your skill is a Hard success, a fifth is Extreme. Bonus and penalty dice add an extra tens die and keep the better or worse. Warhammer Fantasy Roleplay 4e: roll under your skill; the difference in tens gives Success Levels. Mothership: d100 under your stat; doubles are criticals.
Dice pools
Blades in the Dark: roll a pool of d6s and take the highest die. 6 is a full success, 4–5 partial, 1–3 a bad outcome; two 6s is a critical. Shadowrun: roll a pool of d6s; each 5 or 6 is a hit. Rolling 1s on more than half the dice is a glitch. Vampire: The Masquerade 5e: roll a pool of d10s; each 6+ is a success, and each pair of 10s counts as a critical worth four successes. Hunger dice add complications.
2d6 systems
Powered by the Apocalypse games (Apocalypse World, Monster of the Week, Masks): roll 2d6 + stat. 10+ strong hit, 7–9 weak hit (success with a cost), 6− miss. See why in dice probability.
Other mechanics
Fate: four Fate dice (−, blank, +) plus a skill, read on an adjective ladder. Savage Worlds: roll your trait die (d4 to d12) and a d6 Wild Die, keep the higher; maximum rolls "ace" and explode. The target is usually 4.
Rolling any system
The online dice roller covers d2 to d100 pools, and the Rollune app adds custom dice sizes, keep/drop modes and multi-rolls. Learn the shorthand in dice notation explained.
