Is a d20 roller the same as a physical twenty-sided die?

Statistically, yes — each roll is drawn uniformly from 1 to 20 using a cryptographically secure random number generator, so no number is more likely to come up than any other.

Can I roll with advantage or disadvantage?

You can roll two d20s here and read the higher or lower yourself, but this roller adds the dice together rather than keeping one. For advantage or disadvantage handled automatically — rolling twice and keeping the higher or lower result — use the dedicated Advantage/Disadvantage Roller instead.

D20 Roller

A dedicated twenty-sided die roller for tabletop role-playing games. Roll single or multiple d20s with an optional modifier for checks and saves. This is an unofficial fan tool and isn't affiliated with any game publisher.

Number of dice

Modifier

Added to the total

Seed (optional)

Replays the same sequence. Deterministic, not cryptographic.

Show the exact odds for each roll

Your roll will appear here, with the odds of getting it.

✓ The probabilities add up to one — 20 possible totals, from 1 to 20
✓ The average matches the closed form — 1 × (20 + 1) ÷ 2 is 10.5, computed independently of the distribution
✓ The spread matches the closed form — standard deviation 5.77, from each die's own variance of (s² − 1) ÷ 12
✓ The range is what the dice can reach — all ones is 1, all 20s is 20
✓ The distribution is symmetrical about the average — which is why the middle totals are the likeliest — the mode is 1 and 2 and 3 and 4 and 5 and 6 and 7 and 8 and 9 and 10 and 11 and 12 and 13 and 14 and 15 and 16 and 17 and 18 and 19 and 20

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How to use this tool

Choose how many d20s to roll.
Optionally add a modifier.
Roll to see each result and the total.

Worked examples

A skill check with a +5 bonus: Roll 1 d20, modifier +5. A raw 12 becomes 17. The roll and the total are shown separately so you can see whether the die itself came up high.
Rolling for a group of four: Roll 4 d20s at once and read them in order rather than rolling one at a time.

Common use cases

Ability checks and saving throws in tabletop RPGs
Any game that uses a twenty-sided die
Quick random numbers from 1–20

How this generator works

Each d20 is an independent draw of a whole number from 1 to 20, taken from your browser's Web Crypto random generator with the range conversion corrected so no face is favoured. A modifier is added after the roll, never before, so a natural 1 and a natural 20 stay visible as themselves — the tool shows the die result and the adjusted total separately rather than only the sum.

Randomness and fairness

Every die is rolled independently with your browser's cryptographic random number generator, so each face is equally likely and a run of high rolls is a run rather than a trend. The optional seed replaces that with a deterministic, non-cryptographic generator: the same word always produces the same rolls, in the same order. That is useful for a play-by-post game where two people need the identical result, and it is exactly why a seeded roll must never settle anything that matters — the sequence is knowable in advance to anyone holding the word.

For how randomness is produced across the whole site, see how Generate Random works.

Limitations and good to know

The tool rolls dice and nothing else. It does not know your character, your bonuses, or your game's rules, so working out what a result means is still down to you and your table.
Every face is equally likely on every roll. There is no luck balancing and no adjustment based on previous rolls.
Rolls are not saved or shared, so remote players cannot independently verify a roll made on your screen. Groups playing online usually prefer a roller built into their virtual tabletop for that reason.

Unofficial fan tool; not affiliated with any tabletop RPG publisher.

Frequently asked questions

Is a d20 roller the same as a physical twenty-sided die?: Statistically, yes — each roll is drawn uniformly from 1 to 20 using a cryptographically secure random number generator, so no number is more likely to come up than any other.
Can I roll with advantage or disadvantage?: You can roll two d20s here and read the higher or lower yourself, but this roller adds the dice together rather than keeping one. For advantage or disadvantage handled automatically — rolling twice and keeping the higher or lower result — use the dedicated Advantage/Disadvantage Roller instead.