Free Dice Roller and Coin Flip
Roll up to 10 d4, d6, d8, d10, d12, d20 or d100 dice with modifiers, or flip coins and track heads and tails. Uses secure randomness.
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How to roll virtual dice and flip a fair coin
Roll up to ten dice of the same type with a modifier, or flip up to 100 coins at once. Every result uses secure browser randomness and is listed in the history.
- Choose Dice roller or Coin flip.
- For dice, pick the number of dice, a die type from d4 to d100 and an optional modifier from -100 to 100.
- Press Roll to see each die, the total and the possible range.
- For coins, set how many coins to flip at once and press Flip. The tally tracks heads, tails and percentages.
- Review, copy or clear the history of the last 100 rolls and flips.
When virtual dice and coins are useful
Tabletop role playing games, board games and classroom activities often need dice that are not at hand. A virtual roller handles every common polyhedral die, from the four sided d4 to the percentile d100, and adds modifiers so players do not have to do the arithmetic mid game.
Coin flips settle quick decisions, choose who goes first, or make a simple probability experiment for a math lesson. Flipping many coins at once and watching the tally is a fast way to see the law of large numbers in action.
The history keeps the last 100 results with timestamps, which helps when a group wants to check what was rolled a few turns ago.
Worked example: an attack roll, damage and a hundred coins
Suppose a player rolls 3d6+2 and the dice show 4, 1 and 6. The dice sum to 11 and the modifier brings the total to 13. The tool also shows the possible range, from 5 when every die shows 1 to 20 when every die shows 6, and the average result for this roll is 12.5.
A single d20 with a +5 modifier has a range from 6 to 25, and each face from 1 to 20 has a 5 percent chance. In coin mode, flipping 100 coins at once might give 47 heads and 53 tails. That is normal: the chance of getting exactly 50 heads in 100 fair flips is only about 8 percent, even though the long run share approaches 50 percent.
How the randomness works
Each die and coin is generated with crypto.getRandomValues, the browser's cryptographic random source, which produces 32 bit random numbers. Mapping those numbers to a die by taking a remainder could slightly favor some faces, so the tool uses rejection sampling. For a d6 it accepts values below 4,294,967,292, the largest multiple of 6 that fits, and redraws the 4 values above that.
The accepted value is divided by the number of sides and the remainder plus one becomes the face. Coins use the same method with two outcomes. Results are generated on your device and nothing is sent to a server.
A short spin animation plays after each roll, but the numbers are already decided when you press the button. If your device asks for reduced motion, the animation is skipped and the results appear immediately, with the same fairness.
Common mistakes with dice and coin probability
A frequent misconception is the gambler's fallacy, the belief that tails is due after several heads. Each flip and each roll is independent, so past results never change the next one. Streaks of five or six identical flips are common in long sequences.
Another mistake is entering the modifier per die when the game applies it once per roll. This tool adds the modifier once to the total. If your game adds a bonus to every die, multiply the bonus by the number of dice and enter that instead.
Useful tips and limitations
- Use the modifier for bonuses or penalties, such as 1d20+5 for an attack roll.
- Reset the coin tally before starting a new experiment so earlier flips do not mix in.
- Use the copy button on the history to paste a record of rolls into a game chat.
- Flip 100 coins several times to show students how results vary around 50 percent.
Common questions
Are the Dice Roller and Coin Flip results truly random?
They use crypto.getRandomValues with rejection sampling, which gives every face and side an equal chance. That is stronger than the Math.random function many simple rollers use.
Can I roll different dice types together in the Dice Roller?
Each roll uses one die type. For a mixed roll such as 1d8 plus 2d6, roll each group separately and add the totals.
What does the modifier do in the Dice Roller?
It adds or subtracts a fixed number from the sum of the dice. A roll of 3d6+2 with dice showing 4, 1 and 6 totals 13.
Is a d100 in this dice roller the same as rolling two d10 percentile dice?
It gives the same equal chance for every result from 1 to 100. Physical percentile dice are often read with 00 and 0 as 100, which this roller reports directly as 100.
How many coins can I flip at once with the coin flip mode?
Between 1 and 100 coins per flip. The result shows the heads and tails count and the full sequence, and the running tally adds them to earlier flips.
Why does the dice roller show a range under the total?
The range shows the lowest and highest totals possible for that roll, including the modifier, so you can tell at a glance how good or bad a result is.
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