Is an online dice roller really random?

This one draws every die from crypto.getRandomValues, the browser’s cryptographic generator, not from Math.random. Draws that would favor some faces are thrown away and drawn again, so a d20 lands on each face 1 time in 20 over the long run. The line under the history shows the average total and average kept die for this visit: three rolls of 2d6 totalling 27 read 3 rolls, average total 9, average kept die 4.5. A short run drifts from the expected 7 and 3.5; a long one settles near them.

What does 2d6+3 mean?

Roll two six-sided dice, add them and add 3. The number before the d is how many dice, the number after it is the sides, and + or - adds a modifier. 2d6+3 gives 5 to 15 with an average of 10.

How do I roll 4d6 and drop the lowest?

Type 4d6dl1, or the equivalent 4d6kh3 (keep the highest three). The tool rolls four dice, marks the lowest as dropped and totals the other three. Results run from 3 to 18 and average 12.245, against 10.5 for plain 3d6.

How do I roll with advantage or disadvantage?

Type 2d20kh1 to roll two d20 and keep the higher, or 2d20kl1 to keep the lower. Keeping the higher averages 13.825 and keeping the lower 7.175. A single d20 averages 10.5.

What is the average roll of a d20?

10.5. The average of a fair die is (sides + 1) ÷ 2, so a d6 averages 3.5, a d8 4.5, a d10 5.5, a d12 6.5 and a d100 50.5.

Can I roll a d100 or percentile dice?

Yes. Tap d100 or type d%. It rolls one number from 1 to 100. Any other size from 2 to 1,000,000 sides works too: type it in the Sides field.

Dice Roller

Dice roller for d4 to d100 and notation such as 2d6+3 or 4d6dl1 (drop lowest). Shows each die and the total, plus the minimum, maximum and average. How it works

Dice notation

Examples: d20, 2d6+3, 4d6-1, d% (a hundred-sided die), 4d6kh3 (keep the highest three), 4d6dl1 (drop the lowest one). The fields below follow the notation and the notation follows the fields.

Count

Sides

Modifier

Keep or drop dice

Rolls 1 six-sided die: results from 1 to 6, each equally likely.

Minimum: 1
Maximum: 6
Average: 3.5

Rolls use the browser's cryptographic random generator; each face is equally likely.

Recent rolls

Your last 10 rolls appear here. They are kept in memory only and are gone when you leave the page.

About the Dice Roller

Type dice notation such as 2d6+3, or tap a die from d4 to d100, and press Roll Dice. This dice roller draws every die from the browser’s cryptographic random generator, shows each die and the total, and states the minimum, maximum and average of the roll: 2d6 averages 7 and a d20 averages 10.5.

Minimum, maximum and average of common dice rolls

Notation	What it rolls	Minimum	Maximum	Average
d4	One 4-sided die	1	4	2.5
d6	One 6-sided die	1	6	3.5
d8	One 8-sided die	1	8	4.5
d10	One 10-sided die	1	10	5.5
d12	One 12-sided die	1	12	6.5
d20	One 20-sided die	1	20	10.5
d%	One 100-sided die	1	100	50.5
2d6	Two 6-sided dice	2	12	7
3d6	Three 6-sided dice	3	18	10.5
4d6dl1	Four 6-sided dice, lowest dropped	3	18	12.245
1d20+5	One 20-sided die plus 5	6	25	15.5
2d20kh1	Two 20-sided dice, higher kept	1	20	13.825
2d20kl1	Two 20-sided dice, lower kept	1	20	7.175
8d6	Eight 6-sided dice	8	48	28

Averages of plain dice are exact. Averages of keep and drop rolls are rounded to three decimals.

Frequently asked questions

Is an online dice roller really random?: This one draws every die from crypto.getRandomValues, the browser’s cryptographic generator, not from Math.random. Draws that would favor some faces are thrown away and drawn again, so a d20 lands on each face 1 time in 20 over the long run. The line under the history shows the average total and average kept die for this visit: three rolls of 2d6 totalling 27 read 3 rolls, average total 9, average kept die 4.5. A short run drifts from the expected 7 and 3.5; a long one settles near them.
What does 2d6+3 mean?: Roll two six-sided dice, add them and add 3. The number before the d is how many dice, the number after it is the sides, and + or - adds a modifier. 2d6+3 gives 5 to 15 with an average of 10.
How do I roll 4d6 and drop the lowest?: Type 4d6dl1, or the equivalent 4d6kh3 (keep the highest three). The tool rolls four dice, marks the lowest as dropped and totals the other three. Results run from 3 to 18 and average 12.245, against 10.5 for plain 3d6.
How do I roll with advantage or disadvantage?: Type 2d20kh1 to roll two d20 and keep the higher, or 2d20kl1 to keep the lower. Keeping the higher averages 13.825 and keeping the lower 7.175. A single d20 averages 10.5.
What is the average roll of a d20?: 10.5. The average of a fair die is (sides + 1) ÷ 2, so a d6 averages 3.5, a d8 4.5, a d10 5.5, a d12 6.5 and a d100 50.5.
Can I roll a d100 or percentile dice?: Yes. Tap d100 or type d%. It rolls one number from 1 to 100. Any other size from 2 to 1,000,000 sides works too: type it in the Sides field.

What you can roll

Dice for board games and tabletop RPGs. Tap d4, d6, d8, d10, d12, d20 or d100, or type notation: d20, 2d6+3, 4d6-1, d% for a hundred-sided die, 4d6kh3 to keep the highest three or 4d6dl1 to drop the lowest one. Press Roll Dice and the page shows each die, marks the dropped ones and gives the total. Your last 10 rolls stay in a list, and a line under it gives the visit's average total and average kept die, to set against the expected one. Clear history resets both.

Before you roll, the tool states the minimum, maximum and average the notation can give, so two damage rolls compare at a glance: 2d6+3 runs from 5 to 15 and averages 10, while 1d12+3 runs from 4 to 15 and averages 9.5.

How the rolls are generated

Each die is a whole number from 1 to the number of sides, drawn from the browser's cryptographic random generator (crypto.getRandomValues). MDN describes its output as cryptographically strong random values from a pseudo-random generator seeded with enough entropy. Bits outside the die's range are thrown away and drawn again, so every face has the same chance.

The statistics are calculated, not simulated:

minimum = dice kept + modifier
maximum = dice kept × sides + modifier
average of plain dice = dice × (sides + 1) ÷ 2 + modifier

So 3d6 averages 3 × 7 ÷ 2 = 10.5 and 1d20+5 averages 15.5. For keep and drop rolls the average is worked out from the probability of every outcome and shown to three decimals, for dice of up to 1,000 sides and rolls of up to 500,000 dice × sides.

Limits: 1 to 1,000 dice, 2 to 1,000,000 sides and a modifier between -1,000,000 and 1,000,000. A link that carries dice, such as the one the site search makes for roll 2d6, fills in the fields and waits for you to press the button. Rolls and the visit averages are kept in memory only.

Related Tools

View all tools

Misc

Coin Flipper

Flip 1 to 10 virtual coins for heads or tails, with a running tally. Each face comes from the browser's secure random source, so both sides are equally likely.

Misc

Random Number Generator

Random number generator: draw 1 to 10,000 numbers between a minimum and maximum you set, as whole numbers or decimals, with or without repeats, sorted or not.

Misc

List Randomizer

Shuffle a list, pick winners or split it into near-equal groups with the browser's cryptographic random generator: one item per line, up to 10,000 lines.

Misc

Rock Paper Scissors

Play rock paper scissors against a computer that picks at random, with a scoreboard, win rate and streaks. Every round is 1 in 3 to win, lose or draw.

Dev

Random Data Generator

Generate 1 to 1,000 fake people as JSON, CSV or a SQL INSERT: id, name, email, phone, address, age and active, each optional but id. Seeds repeat rows.

Misc

Dice Probability Calculator

Odds of an exact, at-least or at-most total on 1 to 100 dice from d4 to d20, of one or every die showing a value, or of a d20 with advantage.

Dice Roller

Use the Dice Roller

Recent rolls

About the Dice Roller

Minimum, maximum and average of common dice rolls

Frequently asked questions

What you can roll

How the rolls are generated

Related Tools

Coin Flipper

Random Number Generator

List Randomizer

Rock Paper Scissors

Random Data Generator

Dice Probability Calculator