Roll d20 and D&D dice without hiding the table rule.

Flat d20 checks

Use 1d20 when the table needs one unmodified twenty-sided result. Use 1d20+5 or 1d20-1 when the rule adds a fixed modifier. The receipt keeps the individual d20 visible, so the natural die and the modified total are not confused.

Declare the purpose before the roll: “I am rolling 1d20+4 for this check.” That sentence gives everyone the notation and modifier before the result can influence the explanation.

Roll a d20

Attacks, saves and initiative

The same d20 notation can represent different table jobs. An attack might use 1d20+7 against armor class, a saving throw 1d20+3 against a difficulty class, and initiative 1d20+2 to order a combat round. The roller performs the arithmetic; it does not know which game rule decides success.

Keep the target number and any situational bonus outside the tool unless the table has already agreed to include them in the modifier. This prevents a correct total from disguising an incorrect rule.

Damage rolls

Damage often uses several dice and a modifier rather than a d20. Examples include 1d8+4, 2d6+3 and 8d6. Each die remains visible in the result detail, which makes an unexpected total easier to inspect.

The notation parser supports one dice group with an optional integer modifier. It does not resolve conditional rerolls, exploding dice, damage types or “roll twice and keep the better total” automatically. Apply those game rules at the table.

4d6 drop lowest

For the common ability-score method, roll 4d6, discard the lowest individual face, then add the remaining three. A roll of 6, 5, 3 and 1 becomes 14 after the 1 is removed.

The roller keeps all four faces visible but does not discard a die automatically. That makes the table decision inspectable and leaves room for a game master to specify rerolls, minimum totals, fixed arrays or point buy instead.

Advantage and disadvantage

For advantage, enter 2d20 and keep the higher individual d20. For disadvantage, enter 2d20 and keep the lower individual d20. If the dice show 7 and 18, the kept die is 18 for advantage and 7 for disadvantage.

The visible total of both dice is not the result of the check. Choose the higher or lower die first, then add the declared modifier. State “advantage” or “disadvantage” before rolling; the current tool does not choose keep-high or keep-low on your behalf.

Natural results and modifiers

A modifier changes the arithmetic total, not the face that appeared on the d20. A natural 20 with a -2 modifier is still a natural 20 and produces a total of 18. A natural 1 with a +8 modifier is still a natural 1 and produces a total of 9.

Whether a natural result has a special consequence depends on the game and the type of roll. The roller deliberately shows both values instead of claiming that every natural 20 is an automatic success or every natural 1 an automatic failure.

D100 and percentile tables

Use 1d100 for the tool's physical 100-sided die. Use 1d100-percentile when the table expects two ten-sided percentile dice. These are separate display methods for a value from 1 to 100; read the d100 guide before switching conventions during play.

Worked table examples

• Perception check: declare 1d20+5, compare the total with the agreed difficulty class.
• Initiative: roll 1d20+2, then record the total with the character name.
• Weapon damage: roll 2d6+3; inspect both d6 faces and the final total.
• Advantage: roll 2d20, keep the higher individual die, then add the declared modifier.
• Disadvantage: roll 2d20, keep the lower individual die, then add the declared modifier.

For more situations, see the worked dice examples and the notation guide.

Method, privacy and limits

The normal WebGL path simulates a throw and reads the uppermost face after the dice settle. The non-WebGL fallback uses the documented logical random generator. The method page explains both paths, notation limits, d100 geometry and the dated verification boundary.

Selections, roll results and the visible history stay in the current browser tab and are not intentionally uploaded as a shared roll record. Standard website requests still reach hosting, security and font providers; the privacy page documents that boundary.

This is an independent general-purpose roller, not an official D&D product, certified random-number service or gambling tool. Use the game rules agreed by the table, and use an audited or regulated process when the outcome has legal, financial or safety consequences.