Dice Roller

When to use it

Board games, role-playing sessions and classroom draws all need a die at short notice, and the physical ones have a habit of disappearing under the sofa. This page rolls one to twenty dice of any size from four to nine hundred and ninety-nine sides, shows each face, and adds an optional modifier to the total.

Each roll uses your browser's cryptographic random generator, so every face has the same chance and nothing is sent anywhere. The result is not reproducible: pressing the button again produces a genuinely new roll.

How the maths works

Each die is drawn uniformly from 1 to its number of sides, independently of the others. The total is the sum of the faces plus the modifier, which is applied once, not once per die. A notation like 3d8 means three dice with eight sides each, so the range is 3 to 24 before any modifier.

The average of a single die with s sides is (s + 1) ÷ 2, which is why a d6 averages 3.5 and 2d6 average 7. The range is symmetric around that value, but a single roll is just as likely to land at either end.

A worked example

The defaults roll 2d6 with no modifier.

1. Die one comes up 1, die two comes up 6.
2. Dice sum: 1 + 6 = 7.
3. Modifier is zero, so the final total is 7.
4. The table lists each die and its face, so a mistyped count is easy to spot.

Seven is the most likely total for 2d6, because more combinations produce it than any other number: six of the thirty-six pairs.

Dice at a glance

Doubling the sides does not double the typical result in a single roll: it doubles the average, which is a different statement.

Common mistakes

• Expecting the dice to remember. A run of low rolls does not make a high one more likely; each roll is independent.
• Applying the modifier per die. A +2 on 3d6 adds two to the total, not six.
• Reading 2d6 as twenty-six. The notation counts dice, not digits; 2d6 is two six-sided dice.
• Assuming a fair die beats the house. The rolls are fair, but games built on them are priced to favour the operator. No tool changes that.

Keep exploring

• Probability Calculator — the chance of a total, and of at least one success.
• Random Number Generator — numbers from any range, with or without repeats.
• Odds to Probability Calculator — what a payout implies about the chance behind it.