Free Plinko SimulatorA Galton board probability lab for the classroom.

A Galton board (also called a bean machine or quincunx) is a board with rows of pegs. Balls dropped from the top bounce left or right at each peg and collect in slots at the bottom, where they build up a bell-shaped curve. It shows how many small random steps add up to a binomial distribution that looks like a normal distribution.

Yes. Every feature is free with no sign-up and no watermark: as many balls and runs as you like, PNG, CSV and video export included. It runs in your browser, so it also works well on classroom computers and tablets.

With n rows and a fair 50/50 bounce at every peg, the slot a ball lands in is the number of times it went right: a binomial distribution with mean n/2 and standard deviation √n/2. As n grows, that distribution approaches the normal curve, which is the central limit theorem at work.

Real physics simulates every bounce of the ball off the pegs and walls, like a wooden board on a desk. The ideal model flips a fair coin at every peg, so its results follow the binomial distribution exactly. Comparing the two is a good way to talk about models and real-world measurements.

They compare the counts you observed in each slot with the counts the ideal 50/50 model expects. A large p-value means the results are consistent with the model; a small one (below 0.05) means the board is behaving measurably differently. Slots that expect very few balls are grouped together first, as the test requires.

Yes. Fast-forward drops 1,000 or 10,000 balls at once using the same physics at full speed, so a smooth histogram takes seconds. The ideal model is instant.

Download the histogram as a PNG chart or as a CSV with the count, share and expected count of every slot, ready for a spreadsheet. You can also export an MP4 or WebM video of the board filling up, with sound, in vertical, square or widescreen format for slides and social media.

Every run uses a seed. Type the same seed with the same settings and the balls follow the same paths again, on any computer. Press the dice button for a fresh seed.