D100 Roller
Roll a virtual d100 — a percentile roll — made with two d10s (tens and units), not a 100-faced sphere. Every face lands with an equal 1-in-100 probability and an average roll of 50.5, generated with cryptographic randomness in your browser. A 'd100' is almost never a physical 100-sided ball (those exist as novelties and roll forever); it is a percentile roll of two d10s, one read as tens and one as units, giving exactly 100 equally likely results from 1 to 100. This page rolls true percentile values directly, so each number has a precise 1% probability.
D100 Roller reference last updated · reference source
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Dated static reference; no live data is fetched. Verify current source values and assumptions before relying on results.
What this tool does
Roll a virtual d100 — a percentile roll — made with two d10s (tens and units), not a 100-faced sphere. Every face lands with an equal 1-in-100 probability and an average roll of 50.5, generated with cryptographic randomness in your browser. A 'd100' is almost never a physical 100-sided ball (those exist as novelties and roll forever); it is a percentile roll of two d10s, one read as tens and one as units, giving exactly 100 equally likely results from 1 to 100. This page rolls true percentile values directly, so each number has a precise 1% probability.
How to use the D100 Roller
- Check Sides per die: 100.
- Check Dice count: 1.
- Review the D100 Roller result and its exact-value comparison table.
- Verify assumptions before applying the result.
Formula
each die is a uniform integer from 1 through sides, using Web Crypto
- sides
- Sides per die
- count
- Dice count
Independent virtual dice. Generate again to reroll.
Worked example
D100 Roller: Sides per die = 100; Dice count = 1. Roll a virtual d100 — a percentile roll — made with two d10s (tens and units), not a 100-faced sphere. Every face lands with an equal 1-in-100 probability and an average roll of 50.5, generated with cryptographic randomness in your browser. A 'd100' is almost never a physical 100-sided ball (those exist as novelties and roll forever); it is a percentile roll of two d10s, one read as tens and one as units, giving exactly 100 equally likely results from 1 to 100. This page rolls true percentile values directly, so each number has a precise 1% probability.
Inputs
- Sides per die100
- Dice count1
Result
- Total35
- Rolls35
- Expected total (average over many rolls)50.5
- Minimum possible total1
- Maximum possible total100
- Chance of the maximum total1%
- Chance each single die shows its top face1%
D100 quick odds
| Question | Answer |
|---|---|
| Average roll | 50.5 |
| Chance of any single face | 1 in 100 (1%) |
| Chance of rolling the maximum (100) | 1 in 100 |
| Chance of rolling above the average (over 50.5) | 50 in 100 (50%) |
| Faces | 100 |
Results explained
- Total
- The sum of the independent d100 rolls shown, each a uniform integer from 1 to 100.
- Rolls
- The individual die results in the order rolled.
- Expected total (average over many rolls)
- Dice count × 50.5, the theoretical average for a d100.
- Chance of the maximum total
- The probability that every die in the roll shows 100 at once: (1/100)^count.
Frequently asked questions
Percentile dice drive Call of Cthulhu, RuneQuest and the BRP family, where skills are percentages and you roll at or under them; Warhammer Fantasy Roleplay and Zweihänder use the same roll-under-percentile engine, and classic RPG tables (wild magic, treasure, weather) are written as d100 charts.
(100 + 1) ÷ 2 = 50.5. Every face from 1 to 100 is equally likely, so the long-run average sits exactly halfway between the minimum and maximum.
Exactly 1 in 100, or 1%, on a single die. With two dice both showing 100 the chance drops to 1 in 10000 (0.01%).
Yes. Rolls come from the Web Crypto API with rejection sampling, so no face is favoured by modulo bias, and nothing is weighted, seeded from the clock or influenced by previous rolls.
Percentile rolls make probabilities transparent: a 73% skill fails exactly 27 times in 100, and rolling doubles like 44 or 77 is often a critical in BRP games — there are nine doubles (11, 22, … 99) in 1–100.
Yes — raise the dice count (gamers write that as 2d100, 3d100 and so on). Totals then follow a bell curve centred on 50.5 per die: extremes get rarer as you add dice, which is why multi-dice rolls feel more predictable than a single big die.