The d10, properly introduced
There is no ten-faced Platonic solid, so the d10 is a pentagonal trapezohedron: ten kite-shaped faces meeting at two points. It earns its place because we count in tens. Roll two of them and you get a percentile throw, 1 to 100, which is how RPGs have resolved skill checks since the late 1970s. Its faces read 0 through 9, with 0 conventionally counted as ten.
Roll it for: percentile rolls, paired as tens and units; random digits, one at a time; any 1-in-10 decision. And if the d10 isn't the die your game asks for, the full dice roller has the other five.
Every throw comes from your browser's cryptographic generator through rejection sampling, which is why each of the 10 faces lands at exactly 10% rather than approximately. How random is random covers why the daily numbers elsewhere on this site are deliberately drawn the opposite way.
- 10, numbered 1 to 10
- Pentagonal trapezohedron, not a Platonic solid
- 10% — exactly 1 in 10
- 5.5
- averages 11; totals range 2 to 20
- two 10s in a row: 1 in 100
D10 — frequently asked
A 10-sided die shaped as a pentagonal trapezohedron, the one standard die that is not a Platonic solid. The only die in the standard set that isn't a Platonic solid. Faces are numbered 1 to 10, and on a fair d10 each lands with exactly a 10% chance.
One in 10, or 10%, the same as every other face. Rolling two 10s back to back happens once in 100 attempts. The roller here uses rejection sampling on a cryptographic generator, so those odds hold exactly.
5.5. A fair die averages the midpoint of its range, so 2×d10 averages 11 and 3×d10 averages 16.5. Single rolls are flat: an average result is no more likely than a 10 or a 1.
Percentile rolls, paired as tens and units; Random digits, one at a time; Any 1-in-10 decision. Beyond those, any decision with 10 options maps onto it directly.