Dice probability calculator

Exact odds for any dice expression — from 2d6 to 4d6-keep-highest-3 and d20 advantage — with the full distribution chart.

Free, no sign-up

Before you use it

Works well for

  • Exact odds for tabletop and video game dice
  • Advantage, disadvantage and keep-highest rolls
  • Balancing checks and combat in game design

Not the right tool for

  • Exploding dice, rerolls and custom dice faces
  • Very large dice pools with keep-highest (limited to stay fast)

Supported notation

  • 2d6, 1d20+5, 1d8+1d6+3, d% (d100)
  • 4d6kh3 — roll 4d6, keep the highest 3 (classic ability scores)
  • 2d20kh1 / 2d20kl1 — advantage and disadvantage

Probabilities are calculated exactly, not by simulation. The highlighted bars are results at or above your target.

For game designers

Use it to balance combat and skill checks: compare how swingy 1d20 is against the bell curve of 3d6, or how much advantage really helps (about +3.3 on average, more near the middle of the range).

Frequently asked questions

How do I get the chance of rolling exactly a number?

Hover over its bar in the chart.

Why does a big expression fail?

Keep-highest rolls are calculated by listing every combination, so very large pools are limited to keep your browser fast.

Is the "Roll it" button fair?

Yes, it uses your browser's cryptographic random generator and the exact distribution.