About this tool
The Dice Pool Success Calculator finds your odds in success-counting systems like Shadowrun, World of Darkness and other Storyteller games, computed in your browser with nothing uploaded. Enter how many dice you roll, how many sides each has, the target a die must meet to count, and how many successes you need.
The chance any one die succeeds is p = (sides − target + 1) / sides — for a d6 needing 5 or more that is (6 − 5 + 1)/6 = 1/3. The number of successes follows a binomial distribution, so the probability of getting at least S successes is the sum from k = S to N of C(N, k)·p^k·(1 − p)^(N − k). Binomial coefficients are computed with log-factorials for stability at large pools. Alongside that it reports the expected number of successes, N·p, and the chance of zero successes, (1 − p)^N — the botch or glitch case in many systems.
This is the straightforward pool model: fixed dice, a flat target, and no exploding or re-rolling. If your game explodes dice on their maximum face, treat the result as a close lower bound, since extra rolls can only add successes.