Probability Simulator
Flip coins, roll dice, or spin a spinner up to 10,000 times instantly and watch a live bar chart converge on the true theoretical odds, making the law of large numbers visible.
Built by the AbraCalc team
How to play
- Choose an experiment type — Coin, Die (6-sided), or Spinner — and set the spinner's slice count if you picked that mode.
- Pick how many trials to run per batch, from 1 up to 10,000, using the Trials per run dropdown.
- Tap Run Trials to fire that many real trials at once and watch the bar chart update with the results.
- Compare the teal actual bars against the amber expected-count line, and run more trials to see the bars converge on the theoretical odds.
Pick an experiment — a coin flip, a six-sided die, or a custom spinner with anywhere from 2 to 12 slices — then choose how many trials to run at once, from a single flip up to ten thousand in one batch. Tapping Run Trials fires every single one of those trials for real, tallying each result into its own bucket and redrawing a live bar chart where bar height reflects how often that outcome actually landed. A thin marker line sits across each bar showing the theoretical expected count for that many trials, so a class can watch the real teal bars drift toward or away from the mathematical prediction as the sample size grows. Running larger batches makes the law of large numbers visible in real time: small trial counts wobble unpredictably, while ten-thousand-trial runs settle in close to the true odds. Reset clears the tally to start a fresh experiment from zero.
Frequently asked questions
- Does a 10,000-trial run actually simulate 10,000 individual results?
- Yes — every trial in the selected batch size runs as a real random draw and is tallied into its outcome bucket individually; nothing is estimated or extrapolated, which is what lets the chart demonstrate genuine convergence rather than a simulated approximation.
- Why does the expected line move when I change the trial count?
- The expected marker always represents the theoretical count for the total number of trials logged so far, divided evenly across the possible outcomes, so it recalculates and shifts every time you run another batch.
- How many slices can the spinner have?
- The spinner accepts any slice count from 2 to 12; entering a number outside that range is automatically clamped to the nearest valid value so the chart always has a sensible number of bars to display.