Dice Roller for Tabletop RPGs
Digital dice, notation, and why gamers use roll apps
Tabletop role-playing games like Dungeons & Dragons and Pathfinder use a standard set of polyhedral dice — d4, d6, d8, d10, d12, d20, and d100 — each named for its number of faces, and most actions in the game resolve by rolling one or more of them against a target number. A d20 roll is the backbone of the system: attack rolls, skill checks, and saving throws are almost always a d20 roll plus modifiers compared to a difficulty number.
Dice notation is the shorthand used to describe a roll: "3d6+2" means roll three six-sided dice, sum them, and add 2. It shows up constantly in character sheets and spell descriptions, and a good digital roller needs to parse it correctly, not just roll single dice one at a time.
Digital dice use a random or pseudo-random number generator rather than physical momentum and gravity, and for casual tabletop play the fairness is not meaningfully different from physical dice — both can theoretically be biased (loaded dice exist; so do poorly seeded RNGs), but any reasonably implemented digital roller is fine for game use. We built Castral to be the fastest possible tap-to-roll experience at the table, including the natural-20/natural-1 critical detection that D&D 5e attack rolls depend on.
The app
How it compares to other tools
Frequently asked questions
What are the standard tabletop RPG dice?
The core set is d4, d6, d8, d10, d12, d20, and d100 (percentile, usually two d10s read as tens and ones). D&D 5e and most similar systems lean heavily on the d20 for attack rolls, skill checks, and saving throws, with the other dice mostly used for damage rolls.
Are digital dice rollers actually fair/random?
Any reasonably implemented digital roller uses a well-seeded random number generator, which for casual game purposes is at least as fair as physical dice — physical dice can have manufacturing imperfections that create subtle bias, while a correctly implemented digital RNG doesn't. Neither is provably perfect, but both are fine for tabletop play.
What does dice notation like 2d6+3 mean?
The number before "d" is how many dice to roll, the number after is how many sides each die has, and anything after a +/- is a flat modifier added or subtracted from the total. "2d6+3" means roll two six-sided dice, add them together, then add 3 to the result.
What is a critical hit or critical fail?
In D&D 5e and similar systems, rolling a natural 20 on a d20 attack roll is a critical hit (typically doubling damage dice), and rolling a natural 1 is an automatic miss or critical failure. "Natural" means the raw die result before modifiers — a natural 20 counts even if modifiers would have made a lower roll succeed too.