Science & Engineering

Dice Probability Calculator (Exact Odds)

Enter a number of dice and sides and it computes the exact chance of hitting a sum, whether you want exactly that total, at least it, or at most it. It enumerates every outcome rather than estimating.

Reviewed and updated

How to use
  1. Set the number of dice and the number of sides.
  2. Enter the target sum you care about.
  3. Choose exact, at-least, or at-most, then read the probability.
Target
Probability of the total

Favorable
Total outcomes
Expected mean
Std deviation
For study and estimation. Verify against authoritative data before relying on a result.
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Every roll is favourable outcomes over total outcomes

A fair die with s sides has each face equally likely. Roll n of them and there are sn equally likely results — 6×6 = 36 for two ordinary dice. The probability of any total is just how many of those results reach it, divided by the whole count.

P(total) = favourable outcomes ÷ sn

Totals bunch in the middle

The extremes need one exact pairing each; the middle totals can be reached many ways. That is why 7 sits at the peak for two dice and the edges are rare.

2 or 121/36
4 or 103/36
6 or 85/36
76/36

Two six-sided dice: the chance climbs steadily to a peak at 7, then falls away symmetrically. Add more dice and the shape tightens into a bell curve.

Two six-sided dice — every total

TotalWaysProbability
211/36 ≈ 2.8%
322/36 ≈ 5.6%
433/36 ≈ 8.3%
544/36 ≈ 11.1%
655/36 ≈ 13.9%
766/36 ≈ 16.7%
855/36 ≈ 13.9%
944/36 ≈ 11.1%
1033/36 ≈ 8.3%
1122/36 ≈ 5.6%
1211/36 ≈ 2.8%

"At least" and "at most" just sum the rows from that total outward — for example "at most 4" is 1 + 2 + 3 = 6/36.

Averages and spread by die

  • Expected value. One fair die averages (s + 1) ÷ 2 — that is 3.5 for a d6. For n dice the mean total is n times that, so two d6 average 7 and three d6 average 10.5.
  • Spread. A d20 (standard deviation about 5.77) scatters far more than a d6 (about 1.71), which is why a d20 roll feels so much swingier.
  • More dice, tighter curve. Sums of many dice pile up near the mean, so extreme totals get rare fast — the central limit theorem at work.

Common questions

What is the probability of rolling a 7 with two dice?

Six of the 36 equally likely outcomes add up to 7, so the chance is 6 in 36, which is 1 in 6, or about 16.7%. Seven is the single most likely total on two six-sided dice.

Why is 7 more likely than 2 or 12?

A total of 2 needs both dice to show 1, and 12 needs both to show 6 — one combination each. A 7 can happen six different ways (1-6, 2-5, 3-4 and their reverses), so it comes up six times as often.

How do I find the chance of rolling at least a certain total?

Add up the outcomes for that total and every higher one, then divide by the total number of outcomes. For "at least 10" on two dice: 3 + 2 + 1 = 6 outcomes out of 36, which is 1 in 6.

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