Plinko Probability: Galton Board
Drop balls through pegs and watch the bell-shaped binomial distribution build, with the theory curve.
Drop balls and watch the bell curve build. Click pegs to remove them, change the number of rows and the chance of going right, switch between counts, percentages and cumulative charts, add the theory curve, and play the payoff game to compare your winnings with the expected value.
About the Plinko Probability: Galton Board
Free plinko probability: galton board. Drop balls through pegs and watch the bell-shaped binomial distribution build, with the theory curve. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for math, the plinko probability: galton board runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Drop balls through pegs and watch the bell-shaped binomial distribution build, with the theory curve. Use it to explore math ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Plinko Probability: Galton Board
- Use the controls to change Rows of pegs, Chance of going right, Ball speed, Chart, Theory curve, and more. The simulation reacts instantly.
- Pick an option such as Counts, Percent, Cumulative, Binomial + normal to switch modes or load an example.
- Press "Drop 1", "Drop 10", "Drop 100", "Restore pegs" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Drop 50 balls at once.
- Bias the chance to 0.8.
- Add more rows.
Key ideas you can learn
- Each peg is a 50/50 (or biased) choice.
- Many random choices make a bell curve.
- Mean = rows × probability.
- More balls match the theory curve better.
Where this is used in the real world
The same maths underlies polling, quality control, insurance and the spread of test scores.
Who is this simulation for?
Algebra, geometry, trigonometry and calculus students, teachers preparing demonstrations, and self-learners who want to see the maths move.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is a Galton board?
A board with rows of pegs where balls bounce left or right at random, showing the binomial distribution.
Why does a bell curve appear?
There are many more ways to reach the middle bins than the edge bins.
Is the Plinko Probability: Galton Board free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Plinko Probability: Galton Board work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.