Dice Roller · Practical guide
D20 Dice Roller with Modifier
Roll a twenty-sided die, add your attack or skill bonus, and see the final total instantly.
At a glance
How a D20 Roll Works
In D&D and most d20 systems, a check is 1d20 + your modifier compared against a target number. Roll the die, add your bonus, and you hit or succeed if the total meets or beats the target. Set the roller above to 1 die, 20 sides, and type your modifier into the modifier field — the result box shows the raw roll and the total after your bonus.
Interactive tool
Dice Roller
Enter your own values, then compare the result with the examples below.
Roll Result
History (Last 10)
Worked Example: Attack Roll
Your fighter has a +5 attack bonus and swings at a goblin with Armor Class 15. You need the die to show 10 or higher (10 + 5 = 15), so 11 of the 20 faces succeed — a 55% chance to hit. Against AC 18 you need a 13 or better, which drops to 40%. A natural 20 always hits and usually crits; a natural 1 always misses.
Common D20 Modifier Scenarios
| Roll | Setup | Typical Target |
|---|---|---|
| Attack roll | 1d20 + attack bonus | Enemy AC (10-20) |
| Skill check | 1d20 + skill modifier | DC 10 (easy) to 20 (hard) |
| Saving throw | 1d20 + save bonus | Spell or trap DC |
| Initiative | 1d20 + Dexterity modifier | Highest total goes first |
Rolling Damage After You Hit
Damage uses smaller dice with the same modifier logic. A longsword swing is 1d8 + Strength modifier; a fireball is 8d6. Set the dice count and sides to match, add the modifier, and the total updates in one roll. The history panel keeps your last 10 rolls so the whole table can verify what happened.
Frequently Asked Questions
What modifier do I add to a d20 attack roll?
Add your ability modifier (usually Strength or Dexterity) plus your proficiency bonus if you are proficient with the weapon. A level 5 fighter with 16 Strength typically adds +6.
Does a natural 20 always hit?
In D&D 5e rules, a natural 20 on an attack roll always hits regardless of the target's AC, and it counts as a critical hit. A natural 1 always misses.
How do I roll with advantage or disadvantage?
Roll the d20 twice and take the higher result for advantage or the lower for disadvantage. The roll history makes it easy to compare the two results.
Is an online d20 roll fair?
Yes. This roller uses your browser's cryptographically secure random number generator, so each of the 20 faces has an equal 5% chance.