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Dice, odds & random picks

Ledger

Numbers, odds, and chance.

Ledger is the console room after hours: dice rendered as instruments, probability with the math shown, and random draws you can replay with a seed. For game masters, teachers, raffle organizers, and anyone making a call under uncertainty.

01 · Signature experiences

Made to feel like instruments.

5 tools
Live
Dice Roller
d4 to d100 rendered as a 3D console. Advantage, disadvantage, 4d6-drop-lowest — with a cyan HUD and a session telemetry log.
Live
Random Number Generator
Roll integers by the handful with optional seed for reproducibility. Unique, sorted, copy-ready output.
Live
Probability Calculator
Binomial, dice-sum, and combinatorics in one calculator — with the formulas shown.
Live
Coin Flipper
A coin flip with bias slider, running tally, and streak tracker. Surprisingly meditative.
Live
Rubik’s Cube
A playable 3D cube — drag to turn, scramble, and race the clock. Not chance, but it lives here too.
02 · Ready to use

Utilities from the ledger corner.

1 live
03 · What it’s for

What Ledger is for.

Dice, odds & random picks

Ledger is for chance: rolling dice, flipping coins, drawing random numbers, and working out the odds before you commit. It also holds a playable Rubik’s Cube, which isn’t chance but needed a home.

The tools don’t all use the same kind of randomness, and it is worth knowing which is which. The Dice Roller draws from crypto.getRandomValues, the browser’s cryptographic random source. The Coin Flipper and the unseeded Random Number Generator use Math.random, which is statistically even and fine for games and raffles but not for passwords. Give the Random Number Generator a seed and it switches to a predictable generator on purpose, so anyone can rerun the draw and check it. Everything runs in your browser.

Game masters use the dice roller for advantage rolls and 4d6-drop-lowest character stats. Teachers use the coin flipper and the probability calculator to show why ten flips can easily come up 7 to 3. Organizers use the seeded number generator to run a raffle anyone can verify.

Which tool to open

  • Dice Roller Pick it for tabletop rolls: d4 to d100, advantage, disadvantage, 4d6-drop-lowest, and custom modifiers, with a log of every roll.
  • Random Number Generator Pick it to draw up to 1,000 whole numbers from any range, with no repeats if you want them and a seed so the draw can be replayed.
  • Probability Calculator Pick it before the roll, not after: binomial odds, the full sum distribution for up to 10 dice, and nCr and nPr counts.
  • Coin Flipper Pick it to settle a two-way choice, or drag the bias slider to watch how a weighted coin behaves over many flips.
  • Rubik’s Cube Pick it to practice solves without a physical cube. Drag to turn layers, scramble, and chase your saved best time.
04 · Questions

Questions people ask.

4 answers

Are online dice rolls fair?

These are. Each roll comes from crypto.getRandomValues, so every face of a die is equally likely and no roll depends on the one before. You will still see streaks. A run of three natural 1s is unlucky, not broken.

What are the odds of rolling a natural 20?

1 in 20, or 5%, on a single d20. With advantage you roll two and keep the higher, so the chance of at least one 20 is 1 − (19/20)², about 9.75%. With disadvantage both dice have to show 20, which is 1 in 400, or 0.25%.

How do I run a raffle people can verify?

Number the entries 1 to N and publish the list. Announce a seed in public, such as the event name and date. In the Random Number Generator, set the range to 1 to N and the count to the number of prizes, keep Unique values on, turn on Reproducible, and draw. Anyone who enters the same settings and seed gets the same winners in the same order.

Is my roll history saved?

The dice log is kept for the current browser tab and cleared when you close it. Coin flips live only in the open page. The Rubik’s Cube saves your best time and lowest move count in your browser’s local storage. None of it is sent to a server.

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