A little chance. A clear result.
D20 Roller
Make a twenty-sided roll with an optional modifier. Use advantage or disadvantage to roll twice and keep the higher or lower die.
Ready when you are
Choose your dice, then roll
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100% client-side · Browser cryptographic randomness
Roll history 0/100
Latest first. Kept only for this page session.
Your rolls will appear here, ready to copy or export.
What is a d20 roller?
A d20 roller generates a random whole number from 1 to 20, like rolling a twenty-sided die. It is useful for tabletop role-playing checks and any game that calls for a d20. This page starts with one d20 and offers a modifier plus normal, advantage and disadvantage modes. Both dice remain visible when one is discarded, so you can check exactly how the total was calculated.
How to use the d20 roller
- 1
Choose your dice
Select a dice type and the number of dice. Use Custom for 2 to 1,000 sides, or apply an expression such as 2d6+3 under Use dice notation.
- 2
Set the rules for this roll
Add an optional modifier. For one d20, choose normal, advantage or disadvantage. Turn animation off for instant results.
- 3
Roll and read the result
Choose Roll dice or press R when you are not typing in a field. Check the individual faces and total. Discarded dice are marked in d20 modes.
- 4
Keep a record
Copy a single result, copy the history, or save a CSV. The latest 100 rolls stay in this page session until you clear them or leave the page.
D20 advantage and disadvantage, explained
A normal d20 has a 5% chance of showing any particular face. With advantage, roll two d20s and keep the higher value: the chance of a natural 20 becomes 1 − (19/20)² = 9.75%. With disadvantage, keep the lower value: both dice must show 20 to keep a natural 20, a 1/400 or 0.25% chance. Add the modifier after choosing the kept die.
- A natural 20 refers to the die face before modifiers, not a modified total of 20.
- For a +5 check, set Modifier to 5; a kept 14 gives a total of 19.
- The tool calculates rolls. Your game’s rules determine whether the result succeeds.
Why use this free online dice roller?
Ready for a quick roll
Start with one click, use common dice presets, or press R for another throw. Lightweight CSS animation needs no 3D engine or model downloads.
Rolls stay in your browser
No account or remote dice service is required. Random values and session history are generated and processed locally.
Rules you can see
Set sides, quantity and modifiers explicitly. D20 checks show both rolled values and clearly identify the kept die.
A useful record of your session
Copy totals with their individual dice, or export the last 100 rolls as CSV with timestamps, modifiers and kept values.
Dice for board games, tabletop checks and classrooms
- Board-game nights
- Replace a missing die, roll two dice for movement, or use several dice of the same type for a custom game.
- Tabletop role-playing
- Make d20 checks, add a bonus once, or roll a pool such as 8d6 for damage. Apply your game’s rules to the result.
- Probability lessons
- Compare observed dice frequencies with theoretical probabilities. Explore why a pair of dice does not have equally likely totals.
- Everyday choices
- Assign a number to each option before rolling. For two options, use a custom two-sided die or the coin flip tool.
How random dice rolls are generated
The tool uses Web Crypto’s getRandomValues() to obtain random unsigned integers. It rejects the small leftover range that cannot be divided evenly by the number of sides, then maps an accepted value to a face from 1 to N. This rejection-sampling step avoids modulo bias.
Each die is sampled independently, including both dice in advantage and disadvantage modes. The animation shows a result selected before the tumble begins. It cannot be influenced by click timing, and repeated faces are allowed. A short session will not necessarily have balanced counts.
For N fair dice with S sides and a modifier M, the lowest normal total is N + M, the highest is N × S + M, and the expected total is N × (S + 1) ÷ 2 + M. An expected value describes the long-run average, not a guaranteed roll.
5 frequently asked questions about the d20 roller
How does advantage work in this d20 roller?
With one d20 selected, choose Advantage to roll two independent d20s and keep the higher. Disadvantage keeps the lower. The modifier is added once, after choosing the kept die. If both dice tie, one is marked kept and the other discarded; the total is the same.
Is this online dice roller random?
Every face is selected with the browser’s cryptographic random-number generator. Rejection sampling avoids the bias that can occur when mapping random integers to a dice range. Rolls are independent; repeats and streaks are normal. This is not a certified or independently verifiable gaming system.
Are my dice rolls sent to a server?
Dice generation, totals, animation and history run entirely in your browser. The tool does not send your roll values to a server or store them in an account. History is held in page memory and disappears when you reload or leave. Copy or export it first if you want to keep it.
Can I use the dice roller offline or on my phone?
Yes. Once this page has loaded, generating rolls needs no network connection. The controls work on mobile and desktop without an account or app installation. Opening the page for the first time, or reloading it without a cached copy, still requires a connection.
Can I turn off the dice animation?
Yes. Uncheck Animate rolls for an instant result. The tool also respects your device’s reduced-motion preference automatically. Animation only displays the already selected result; it does not influence which face wins.