Dice Probability Calculator
Calculate success odds, likely totals, and roll ranges from common tabletop dice expressions like 2d6+1 or 3d20-2.
Last updated: 2026-03-16
Dice probability calculator
Enter your values
Estimate the odds of hitting a target number from a dice expression and flat modifier.
Chance To Succeed
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Enter a dice pool, modifier, and target number to see the success rate and the most likely totals.
Calculation History(0)
Example calculations
Tap an example to prefill the calculator with sample values.
Classic 2d6 skill check
2d6 + 1 against a target of 9
Useful for PbtA-style moves or any tabletop system that resolves checks with a bell curve.
Result: A little better than a coin flip, with 8 as the most likely total
Warhammer charge
2d6 needing a 9-inch charge
A common tabletop decision where exact odds matter before spending a command re-roll.
Result: Only a minority shot, which makes the re-roll decision clearer
High-stat RPG check
3d6 + 4 against a target of 14
A bigger dice pool with a solid bonus where the distribution tightens around the average.
Result: Comfortably favorable odds with a narrow likely band
How the odds are calculated
The calculator builds the full probability distribution for the dice pool, then reads average, most likely total, and success odds directly from that distribution. That makes the output more useful than just eyeballing the average roll.
Use it when a table decision comes down to whether a target number is realistic. It is especially handy for systems where a small change in the target can swing the odds more than players expect.
Dice probability FAQs
A quick guide to target numbers, bell curves, and when exact odds matter.
Is this using exact odds or an estimate?
It uses an exact probability distribution for the dice expression you enter, then measures how much of that distribution meets or beats the target number.
Can I use this for any tabletop system?
Yes, as long as the roll is a standard sum of dice plus a flat modifier. It works well for RPG checks, charges, morale tests, and other target-number rolls.
Does it handle advantage, exploding dice, or rerolls?
No. This version is intentionally simple and covers straight dice pools only. Rerolls and special mechanics would need a rules-specific calculator.
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