Dice Probability Calculator

Enter the number of dice, number of sides, and a target sum to calculate your dice roll probability. Choose from standard polyhedral dice (d4, d6, d8, d10, d12, d20) or set a custom die type. You get back the exact probability of hitting your target, the percentage chance, and the total number of possible outcomes — plus a chart showing the full probability distribution across all possible sums.

How many dice are you rolling at once?

Only used when Dice Type is set to Custom.

The exact total you want to roll across all dice.

Results

Probability of Target Sum

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Favorable Outcomes

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Total Possible Outcomes

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Probability (Fraction Form)

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Expected Rolls to Hit Target

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Probability Distribution Across All Possible Sums

Results Table

Frequently Asked Questions

How do you calculate dice roll probability?

To calculate dice roll probability, divide the number of favorable outcomes (ways to get your target sum) by the total number of possible outcomes (which is the number of sides raised to the power of the number of dice). For example, rolling a 7 with two 6-sided dice has 6 favorable outcomes out of 36 total, giving a probability of 6/36 ≈ 16.67%.

How many possible outcomes are there from rolling two dice?

When rolling two standard 6-sided dice, there are 6 × 6 = 36 possible outcomes. In general, for n dice each with s sides, the total number of outcomes is s raised to the power n (sⁿ). So two d6 dice give 36 outcomes, while three d6 dice give 216.

When rolling 2 dice, what is the probability of rolling a 7?

There are 6 ways to roll a sum of 7 with two d6 dice: (1,6), (2,5), (3,4), (4,3), (5,2), and (6,1). Out of 36 total outcomes, that gives a probability of 6/36 = 1/6, or approximately 16.67%. This makes 7 the most likely sum when rolling two six-sided dice.

What is probability?

Probability is a measure of how likely an event is to occur, expressed as a number between 0 and 1 (or 0% to 100%). A probability of 0 means the event is impossible, while a probability of 1 (100%) means it is certain. In the context of dice, it tells you how often you can expect a particular outcome over many rolls.

What types of polyhedral dice can I calculate probabilities for?

This calculator supports all common polyhedral dice: the d4 (tetrahedron), d6 (cube), d8 (octahedron), d10 (decahedron), d12 (dodecahedron), and d20 (icosahedron). You can also enter a custom number of sides for any non-standard die. These cover the full Dungeons & Dragons dice set and most tabletop RPG scenarios.

How many times do I need to roll to get a specific result?

The expected number of rolls needed to hit a target result is simply 1 divided by the probability of that result. For example, if the probability of rolling your target is 16.67% (1/6), you would expect to need about 6 rolls on average to see that result. This is shown as 'Expected Rolls to Hit Target' in the calculator results.

Can I always roll a 6 on a die?

Yes — rolling a 6 on a single d6 is always possible, with a probability of 1/6 (≈16.67%). Each roll of a fair die is independent, so previous rolls don't affect future outcomes. There's no guaranteed way to roll any specific number, but given enough rolls, every value will appear roughly in proportion to its probability.

When should I use a dice probability calculator?

A dice probability calculator is useful any time you want to evaluate the odds before making a decision in a game — such as deciding whether to attempt a risky move in a tabletop RPG, or assessing the fairness of a board game mechanic. It's also great for educators and game designers who want to understand or balance random outcomes.

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