How to read percentile dice
Roll two d10s. One is marked 00, 10, 20 ... 90 and gives the tens; the other gives the units. Add them: 30 and 7 is 37. 00 and 0 together is 100, not zero. Some tables use two plain d10s and call one of them the tens die before rolling. The roller above draws both dice and adds them for you.
Where the d100 shows up
- Wild magic. A Wild Magic sorcerer who triggers a surge rolls on a d100 table, and the result can be anything from illusory butterflies and flower petals to a fireball centred on the sorcerer.
- Treasure. The magic item tables in the Dungeon Master's Guide are d100 tables.
- Anything with a percentage. "A 15% chance the bridge gives way" is a d100 roll of 15 or lower.
One number, two dice
Because each die is fair, every number from 1 to 100 comes up exactly one time in a hundred. That is the difference from rolling, say, 2d10 and adding them, which piles results up around 11.
A true d100
Hundred-sided dice exist too: a ball with 100 small faces, read by the number on top. On the 3D table, set d100 to One d100 to throw one instead of two d10s. The roller here follows the same setting, and a d1000 becomes a d10 and a d100.
Your odds on a d100
A percentage roll succeeds on that number or lower, so the chance is the number itself:
| Roll this or lower | Chance |
|---|---|
| 05 | 5% |
| 10 | 10% |
| 25 | 25% |
| 50 | 50% |
| 75 | 75% |
| 95 | 95% |
Hoping for a 100? Each roll is 1 in 100, so it takes a while:
| Rolls | At least one 100 |
|---|---|
| 1 | 1% |
| 10 | 9.6% |
| 25 | 22.2% |
| 50 | 39.5% |
| 69 | 50.0% |
| 100 | 63.4% |
| 200 | 86.6% |
Even 100 rolls only give you about a two-in-three chance of seeing it. The dice calculator works out any other roll, and the d10 page explains the dice the percentile pair is made of.
Questions
What does 1d100 mean?
One roll from 1 to 100, every number equally likely. It is usually made with two ten-sided dice, one for the tens and one for the units, and written d100, 1d100 or d%. The Dice Notation Guide covers the rest.
Is 00 and 0 on a d100 a 0 or a 100?
It reads 100. The tens die reads 00 to 90 and the units die 0 to 9, and 00 with a 0 is the top of the range, never zero. A 00 with a 5 is 5; a 10 with a 0 is 10.
How do I roll a d100 with two d10s?
Say which die is the tens before you roll, then read them in order: a 4 on the tens and a 2 on the units is 42. Two plain d10s work the same way, with a 0 and 0 reading 100.
Is rolling 2d10 the same as a d100?
No. Adding two d10s gives 2 to 20, with 11 the likeliest. Reading them as tens and units gives 1 to 100, each exactly 1%. Percentile tables need the second.
What is the average roll on a d100?
50.5, halfway between 1 and 100. A roll of 50 or lower comes up exactly half the time.
Is this d100 roller random and fair?
Yes. Each roll comes from your browser's cryptographic random number generator, with no bias towards any number. Every result from 1 to 100 is exactly 1 in 100, whether you roll two d10s or one true d100.