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Uses local browser-generated random values.
For casual decisions and simulations only. Not for regulated gaming, lotteries, audits, certifications, or cryptographic key generation.
This tool runs locally in your browser. Inputs and results are not transmitted or retained by BoringToolsKit.
Use this result
Share the current inputs or ask ChatGPT to explain the calculation in context.
What does this calculator estimate?
A fair coin gives each outcome a 50 percent probability per flip. Ten fair flips might produce 6 heads and 4 tails, converging toward 50/50 over many flips.
- Fair-coin probability is 0.5 per flip (Wikipedia).
- Short runs vary; the law of large numbers narrows the deviation over many flips.
- The tool can weight the coin for games where odds are not even.
What coin flips model
A fair coin flip is the simplest random event: two equally likely outcomes. Repeated flips follow the binomial distribution — the count of heads converges toward 50% as flips increase, but short runs vary. The tool simulates this.
Limitations to watch for
Short runs are noisy: 10 flips can easily show 7/3. The 'law of averages' doesn't make a fair coin 'due' a tails — each flip is independent. Weighted coins shift the probability.
How to use it in practice
Use it for decisions, game mechanics, and probability demonstrations. For a real coin, the physical coin and flip style affect the outcome. For unbiased randomness in code, use a proper PRNG.
- Choose the number of flips.
- Optionally set a heads bias.
- Read the results and counts.
How this calculator works
Formula
Simulates fair (or weighted) coin flips, counting heads and tails. A fair coin gives each outcome a 50% probability per flip.
Worked example
10 fair flips might produce 6 heads and 4 tails — the count varies run to run, converging toward 50/50 over many flips.
Assumptions to verify
- Each flip is independent.
- The default is a fair 50/50 coin.
- Results are generated with a uniform RNG.
Frequently asked questions
How do I flip a coin?
Set the number of flips and run it — the tool counts heads and tails.
Is a coin flip really 50/50?
For a fair coin and fair flip, yes — each flip is independent.
Why did I get 7 heads in 10 flips?
Short runs vary widely — 10 flips are noisy; the 50/50 split emerges over hundreds.
Is the coin 'due' for tails?
No — flips are independent; past results don't affect the next one.
Can I use a weighted coin?
Yes — the tool's bias option models a loaded coin.
What is this used for?
Decisions, games, statistics demos, and testing randomness.
Is the RNG fair?
It uses a uniform pseudorandom generator — good for practical purposes.
Cite this tool
BoringToolsKit. “Coin Flip Tool.” boringtoolskit.com/coin-flip/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
Privacy: Inputs and results stay in this browser. Any future sponsored recommendation or advertisement will be clearly labeled and kept separate from the calculation.