2d20 roller: advantage and disadvantage

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Roll 2d20 for advantage and disadvantage

Two twenty-sided dice, rolled together. Tap them, press Roll or hit the Space bar. Both results appear side by side, with their sum above them. In fifth edition fantasy role-playing, that pair is how you roll with advantage (keep the higher die) or disadvantage (keep the lower one).

How much advantage is worth

A single d20 averages 10.5. Keeping the higher of two pushes the average to 13.825; keeping the lower drops it to 7.175. In terms of chances, needing 11 or more succeeds 50% of the time on one die, 75% with advantage and 25% with disadvantage. Needing 15 or more: 30% normally, 51% with advantage, 9% with disadvantage. The effect is largest for middle targets and smallest at the extremes, which is why the rules add 5 to a passive check made with advantage.

Natural 20 with advantage: 9.75%, almost double the 5% of a single roll.
Natural 1 with disadvantage: also 9.75%.
Both dice showing 20: 1 in 400, 0.25%.

When you need the sum instead

Some games and tables add the two d20s together, for a result from 2 to 40 that clusters around 21. The table below gives the exact odds of every sum, grouped by three so it stays readable. Note that 2d20 is not a substitute for a d40: the sum is much more likely to land in the middle than at either end.

For a single roll, go back to the d20 roller. Advantage and disadvantage never stack: two sources of advantage still mean two dice.

Exact odds for 2d20

400 equally likely combinations, counted one by one. Average total: 21.

Total	Ways (of 400)	Chance	This or more
4 or less	6	1.5%	100%
5 to 7	15	3.8%	98.5%
8 to 10	24	6%	94.8%
11 to 13	33	8.3%	88.8%
14 to 16	42	10.5%	80.5%
17 to 19	51	12.8%	70%
20 to 22	58	14.5%	57.3%
23 to 25	51	12.8%	42.8%
26 to 28	42	10.5%	30%
29 to 31	33	8.3%	19.5%
32 to 34	24	6%	11.3%
35 to 37	15	3.8%	5.3%
38 or more	6	1.5%	1.5%

How it works

Your dice are ready
The dice for this page are already on the table, and the sentence under them says how many and how many sides. No setup needed.
Roll them
Tap the dice, press Roll or hit the Space bar. They tumble, land, and the result appears at the top.
Keep, re-roll or switch
Tap a die to keep it while the others re-roll; Release all frees them. To roll something else, tap the number of dice or sides in the sentence.

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The guide

Dice Probability Explained: 1, 2 and 3 Dice, d20 and MoreWhy 7 comes up most, d20 advantage and more

Questions

How do I roll with advantage?

Roll two d20s and keep the higher result. This page rolls both at once and shows them side by side.

What is the chance of a natural 20 with advantage?

9.75%: one minus the chance that neither die shows 20, which is 19/20 × 19/20.

What is the average of 2d20 with advantage?

13.825 when you keep the higher die, against 10.5 for a single d20. With disadvantage, the average is 7.175.

Is this dice roller free?

Yes. It is free to use, funded by advertising, with no account and no app to install.

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