A coin has two sides and one job: be fair. It is not quite fair. A person flipping a coin by thumb lands it on the side it started on about 51% of the time [1][2]. That one percent is where this post lives. Chance is the maths of what the dice do. Luck is the story we tell about…
What Makes a Shape Worth Trusting. Five shapes are perfect. Rather more than five are fair. The difference is the whole story. What Makes a Die Fair The obvious answer is symmetry, and the obvious answer is very nearly right. It matters which symmetry, and the usual assumption asks for far more of it than a die needs. A die…
Five shapes are perfectly regular. Every one of them is in your dice bag, and there will never be a sixth. Why Only Five Pick up a d20 and turn it over in your hand. Every face is the same triangle. Every edge meets its neighbour at the same angle. Every point has the same five triangles crowded around it.…
Nine Solids and What They Are For Every die in the set, one at a time. What it is, what it looks like, and the moment at the table it was made for. Dice are written in dX notation, where d means die and X is the number of sides. Nine shapes cover nearly everything D&D asks you to roll.…
Most players know a d20 when they see one and stop there. The Book of Dice keeps going for 107 pages: where the shapes come from, how the table talks about them, every way to roll, and why we keep coming back [1]. Full disclosure: we wrote it. We rolled for objectivity and got a 1. rpgcreator.net is ours, the…
Rolling Dice, Telling Stories, Creating Legends Some rolls are bookkeeping. Others make the whole table stand up. This guide is about the second kind: five rolls players live for, five rolls DMs can use to surprise themselves, and the real odds behind each one, so you know exactly how unlikely your legend was. Rules come from the 2024 rules in…
Gen Con 2026 ran from July 30 to August 2 at the Indiana Convention Center in Indianapolis, and it was the biggest Gen Con yet. I was not there. I was at my desk in a different hemisphere, refreshing three liveblogs at once and doing the time zone arithmetic every non-American gamer does in early August. (Constitution save against the…
DnD Dice Roller has had its biggest update since it launched. Your dice lines can live on an account instead of in one browser, the save button is gone because the site saves as you go, and you can see, and choose, where your random numbers come from. Here is what changed and how to use it. Your dice lines…
Advantage and disadvantage are two of the most important dice rules in modern Dungeons & Dragons. They are also two of the easiest to explain badly. The rule, from the System Reference Document 5.2.1 (the free 2024 rules text, "Playing the Game", D20 Tests) [1]: Advantage: roll two d20s and use the higher. Disadvantage: roll two d20s and use the…
D&D repeats itself. The same attack, the same damage, the same Constitution save every time the wizard takes an arrow. A preset is a roll you make often enough that rebuilding it wastes a turn. In DnD Dice Roller a preset is a dice line with a label. Name each line, press ++ to duplicate one instead of rebuilding it,…
