Dice Roller & Coin Flip (1-10 Dice, Custom Sides)

What is this dice and coin flip tool?

A tool that rolls 1 to 10 dice at once, with 2 to 100 sides each (any of d4, d6, d8, d10, d12, d20, d100, or a custom count), and can also flip up to 10 coins. Everything runs in your browser, so nothing you do here is sent to a server, and there is nothing to install.

It covers the two things a physical dice bag and a coin usually handle: a number for a board game move or a tabletop RPG check, and a fast, fair two-way call.

How to use it

1. Switch between the Dice and Coin flip tabs
2. For dice, set how many (1 to 10) and how many sides (a d4-d100 preset, or a custom count from 2 to 100)
3. For a coin flip, set how many coins (1 to 10)
4. Press the button. Rolling 2 or more dice also shows the total automatically

Is the result actually fair?

Yes, in the sense that matters for a game: every face and both coin sides come up with equal probability, and each roll is independent of the last. A d6 shows 1 through 6 at 1/6 (about 16.7%) each, a d20 at 1/20 (5%) each, and a coin at exactly 50/50. Three 1s in a row does not change the odds of the fourth roll — that instinct is a well-known bias called the gambler's fallacy, not how independent trials work.

That evenness comes from Math.random(), the browser's general-purpose random number generator, not a cryptographically secure one. For game night or a solo tabletop session that distinction never comes up, since nobody is trying to predict your next roll. It matters once a stake with real value is attached — an office raffle, a cash side bet, anything a participant might be motivated to reverse-engineer. Keep those off any web-based roller, this one included, and use a method built for that purpose instead.

What total is most likely with two dice?

With two standard d6s, 7 is the most common total at 16.7%, because six different pairs add up to it (1+6, 2+5, 3+4, 4+3, 5+2, 6+1). A total of 2 or 12 only has one pairing each, so it lands at just 2.8%.

This is why board games that use two dice, like Catan, treat the middle numbers as the valuable ones: they simply come up more often. Roll 2 or more dice in the tool above and the total updates the same way.

What is the expected value of a die roll?

For a fair die with s sides, the expected value (long-run average) is (s + 1) ÷ 2, and the variance is (s² − 1) ÷ 12. A d6 averages 3.5 with a standard deviation of about 1.71; a d20 averages 10.5 with a standard deviation of about 5.77.

Rolling several dice and summing them keeps the average proportional to the count, but the spread grows only with the square root of it — a d6 rolled once has a standard deviation about 49% of its average, while four d6s summed bring that down to roughly 24%. That is the statistical reason tabletop games often build ability scores from 3d6 or 4d6 instead of a single large die: more dice means results cluster closer to average and extreme rolls get rarer.

Notes

• Dice: 1 to 10 at a time, 2 to 100 sides. Coin flips: 1 to 10 at a time
• Modifiers like the "+3" in "2d6+3" are not added automatically; add them to the shown total yourself
• Results are not saved. Reloading the page clears whatever is on screen
• Need to pick one item from a named list instead of a number? Try the decision wheel. Splitting people into teams is handled by the group maker, and matching people to outcomes one-to-one by the ghost-leg lottery