How to Roll a D20 Online: Single Rolls, Batches, and Advantage

A d20 roll is simple: generate a number from 1 through 20, then apply the rule for the check you are resolving. The useful part of an online roller is not just replacing a physical die. It can roll a batch, apply a modifier, and handle advantage or disadvantage without slowing down the table.

If you already know what you need, roll a D20 now. The rest of this guide explains which setting to choose and how to read the result.

What does 1d20 mean?

Dice notation puts the number of dice before the letter d and the number of sides after it. 1d20 means one twenty-sided die. 4d20 means four separate twenty-sided dice.

The notation tells you what to roll, but the game rule tells you what to keep. Four d20s might be four independent character checks. Two d20s might be two independent results, or they might be an advantage roll where only the higher result counts. Decide the rule first, then choose the matching roll mode.

When to roll 1d20, 2d20, 4d20, or 20d20

Use the quick-count buttons when you want a common batch without adjusting the count slider manually.

• 1d20 is the standard choice for one ability check, saving throw, attack roll, or table lookup.
• 2d20 gives two independent results in Normal mode. In Advantage or Disadvantage mode, the roller keeps the higher or lower result.
• 4d20 is useful when four players make the same group check or when one player needs several independent results.
• 20d20 produces a larger sample for simulations, encounter prep, or a random table that needs many entries at once.

For counts between those presets, enter any whole number from 1 through 20. Each die is rolled separately, so a batch does not change the possible value of an individual d20.

Advantage and disadvantage

Advantage and disadvantage are keep-one rules. Advantage rolls two d20s and uses the higher value. Disadvantage rolls two d20s and uses the lower value. Normal mode keeps the requested rolls as separate results.

Example: the dice show 6 and 17.

• With Advantage, keep 17.
• With Disadvantage, keep 6.
• With Normal, keep both results as two independent rolls.

Do not select a batch of two in Normal mode when the rule calls for advantage; the two screens may look similar, but the meaning of the result is different.

Adding a modifier

A modifier is added after the die result is selected. If a d20 shows 14 and the modifier is +3, the total is 17. If the modifier is -2, the total is 12.

Set the modifier before rolling so the result panel can calculate the total. For advantage or disadvantage, the roller first keeps the correct d20 and then applies the modifier. The modifier does not change which of the two dice is higher or lower.

Practical D&D and TRPG examples

The same roller setup covers several common table situations:

1. Ability check: choose 1d20, set the character’s modifier, and use Normal.
2. Saving throw with advantage: choose Advantage, set the save modifier, and roll. The higher d20 is kept before the modifier is added.
3. Attack with disadvantage: choose Disadvantage and the relevant attack modifier. The lower d20 becomes the base result.
4. Four-character group check: choose 4d20 in Normal mode. Read the four dice as separate character results rather than adding them together.

The game or GM still decides the target number, success rule, critical result, and any exceptional case. The roller supplies the random values and arithmetic; it does not replace the rules for a specific system.

Is an online d20 fair?

This roller generates values in your browser with crypto.getRandomValues, a cryptographically secure random source provided by modern browsers. It does not use a predictable counter or a simple visual animation to decide the number. The animation displays a result that has already been generated by the random engine.

No sign-up is required. Your dice count, modifier, and roll mode can also be restored from a shared link, which is useful when everyone at the table should start from the same setup.

Roll your next check

Open the online D20 roller, choose the number of dice and roll mode, add the modifier, and roll. Use Normal for independent results, Advantage to keep the higher of two, and Disadvantage to keep the lower.