Percentile Dice: How to Roll a d100 with Two d10s

What are percentile dice?

Percentile dice are a pair of ten-sided dice used together to make a number from 1 to 100. One die gives the tens digit and the other gives the ones digit. Rulebooks write this roll as d100 or d%.

Most dice sets include them. A standard seven-dice set has one d10 numbered 0 to 9 and one "percentile" d10 numbered 00, 10, 20 and so on up to 90. Real hundred-sided dice exist, but they are close to spheres, roll for a long time and are hard to read, so almost nobody uses them at the table.

If you don't have the dice handy, the d100 roller gives the same 1 to 100 result in one click. This guide covers how to do it with physical dice.

How do you roll a d100 with two d10s?

1. Take two ten-sided dice and decide which one is the tens die. A percentile die marked 00, 10, 20 up to 90 is the tens die by default.
2. Roll both dice at the same time.
3. Read the tens die as the tens digit (for example 40, or 4 on a plain d10 means 40).
4. Read the other die as the ones digit (0 to 9).
5. Add them together: 40 and 7 is 47.
6. If both dice show zero (00 and 0), the result is 100.

If both of your d10s are plain 0–9 dice, use two different colors and say out loud which color is the tens before you roll. That one habit avoids most arguments.

How do you read percentile dice?

Treat the two dice as two digits of one number. The tens die sets the "decade" and the ones die picks the number inside it.

Why does 00 and 0 equal 100?

A d100 is supposed to give a number from 1 to 100, not 0 to 99. Two d10s naturally produce 100 different combinations, from 00+0 up to 90+9. If you read them literally you get 0 to 99. The convention fixes this by moving the one result that would be 0 to the top and calling it 100.

Because exactly one combination of the two dice maps to each number from 1 to 100, every result still has the same chance:

• Any single number: 1 in 100, or 1%.
• Rolling 100 exactly: 1%, the same as rolling 37.
• Rolling 01–05: 5%, five results out of 100.
• Rolling 51 or higher: 50%.
• Average roll: 50.5, the midpoint of 1 and 100.

What about a roll of 0 to 99?

A few games outside D&D read 00+0 as 0 and use a 0–99 range. D&D and most d100 tables assume 1–100. If a table starts at 01 and ends at 00 or 100, use the 1–100 reading.

What are the most common percentile dice mistakes?

• Not choosing the tens die first: with two plain d10s, a 3 and an 8 could be 38 or 83. Pick before you roll, not after you see the numbers.
• Reading 00 and 0 as 0: it is 100.
• Reading 10 and 0 as 100: it is 10. Only double zero is 100.
• Adding the dice like normal dice: a plain 4 and a plain 6 is 46 (or 64), not 10. Percentile dice are read as digits, not summed, unless one die is already marked in tens.
• Using a d10 marked 1–10: some d10s show 10 instead of 0. Treat the 10 as 0 when it is the ones digit, and as 00 when it is the tens digit.

Where do you use a d100 in D&D?

D&D 5e saves the d100 for random tables where a DM wants fine control over how likely each entry is. A result that covers 01–05 has a 5% chance, while one that covers 06–60 has 55%.

• Wild Magic Surge: Wild Magic sorcerers roll on a d100 surge table when a surge triggers. You can roll on one with the wild magic table.
• Treasure and magic items: the Dungeon Master's Guide uses d100 tables for treasure hoards and magic item tables. The loot generator handles random loot for you.
• Trinkets: the Player's Handbook trinket table is rolled with a d100.
• Random encounters and DM tables: many published adventures and homebrew tables use d100 so rare events can be set at 1% to 5%.

How do you use a d100 to check a percent chance?

Any time something has a stated percent chance, a d100 is the most direct way to settle it. Decide the target first, then roll: if the result is equal to or lower than the percentage, the event happens.

• 25% chance: it happens on 1–25 and fails on 26–100.
• 10% chance: it happens on 1–10. On the dice that's a tens die of 00 with any ones die from 1 to 9, plus 10 and 0.
• 1% chance: it happens only on a 1 (00 and 1).

Rolling low for success keeps things readable. You can also roll high and succeed on 76–100 for a 25% chance; the odds are the same as long as you agree before the roll.

Can you roll a d100 with one d10?

Yes. Roll the d10 twice. The first roll is the tens digit and the second is the ones digit, and 0 then 0 still counts as 100. It's slower but gives exactly the same odds. You can do the same thing with the d10 roller, though the d100 roller does it in a single step.

Is a d100 the same as 1d100 or d%?

Yes. d100, 1d100 and d% all describe the same 1 to 100 roll. See the dice notation guide for how the other codes work.

FAQ

Is 00 and 0 on percentile dice 0 or 100?

It is 100. Under the usual convention a d100 rolls from 1 to 100, so a 00 on the tens die and a 0 on the ones die is read as 100, never as 0.

What is 00 and 5 on percentile dice?

00 and 5 is 5. The 00 on the tens die only means 100 when the ones die also shows 0.

Can you roll a d100 with one d10?

Yes. Roll it twice, deciding in advance that the first roll is the tens digit and the second is the ones digit. A 0 then 0 is read as 100.

Are percentile dice fair?

Yes, if the two d10s are fair. Each of the 100 tens-and-ones combinations maps to exactly one number from 1 to 100, so each result has a 1% chance.

What is d% in D&D?

d% is another way to write d100, a roll from 1 to 100. Rulebooks and random tables use both forms for the same roll.

Related

• Roll a d100
• Roll a d10
• Dice Notation Guide: What 2d6+3 Means and How to Read Any Roll
• Wild Magic Surge Table