This coin flip calculator flips fair virtual coins — one or a hundred at a time — tallying heads and tails, tracking streaks, and showing the exact probability of what just happened.
Every specific sequence of 10 flips has probability 1/1,024 ≈ 0.098% — including perfectly alternating HTHTHTHTHT and all-heads. What differs is how many sequences share the same heads-count: the split probability shown uses the binomial coefficient (see the Probability Calculator). Streaks feel rigged but aren’t: a run of 5+ appears in most 20-flip sessions — randomness is clumpier than intuition.
A Fair Coin Is a Binomial Machine
Each flip is independent at 50/50; runs of n flips follow the binomial distribution — the machinery our Binomial Distribution Calculator formalizes and the Probability Calculator generalizes. Part of our Other Calculators collection.
Probability Landmarks (Verified)
- All heads in 10 flips: (1/2)¹⁰ = 1/1,024 ≈ 0.098% — rare per attempt, guaranteed eventually across enough sessions (expect one per ~1,024 tries)
- Exactly 5 heads in 10 (the most likely split): C(10,5)/1,024 = 252/1,024 ≈ 24.6% — still less likely than not: most single sessions land near, not on, the center
- The expected longest streak in 100 flips is about 6–7 — a run of 6 heads in a long session is normality wearing a suspicious costume (the clustering illusion, live)
- Gambler’s fallacy detector: after 9 heads, the 10th flip remains exactly 50/50 — independence means the coin has no memory to balance (see our Random Number Generator for the digital cousins)
Fairness Footnotes
- Physical coins carry tiny biases (the heavier side settles down slightly more; vigorous flips start-side bias ≈ 51% per Persi Diaconis’s work) — this tool uses a cryptographic-grade fair 50/50 for clean mathematics.
- Best-of-series decisions (flip best of 3) exist to wash out single-flip variance — and to give sore losers a structure.
- For decisions that matter, generate the flip before knowing which side you want — the moment of the toss reveals preferences better than the outcome does.
Related Tools
- Binomial Distribution Calculator — the math of many flips
- Random Number Generator — numbers instead of coins
- Other Calculators — the full collection
Frequently Asked Questions
What is the probability of flipping 10 heads in a row?
(1/2)¹⁰ = 1 in 1,024 ≈ 0.098%. Identical math for 10 tails or any one pre-specified sequence — including alternating patterns. This tool’s streak counter shows how unremarkable shorter runs (4–6) are inside longer sessions.
Is an online coin flip really random?
This one uses the browser’s Math.random (a quality pseudorandom generator) at exactly 50/50 per flip — statistically indistinguishable from fair for any practical or classroom purpose. Physical tosses, ironically, are measurably less fair (same-side bias around 51%).
After many heads, is tails “due”?
No — that’s the gambler’s fallacy. Independent flips don’t remember: the next flip is 50/50 regardless of history. What regresses over time is the proportion (a long run dilutes the streak’s share), never because the coin compensates. If results genuinely skew over thousands of flips, suspect the coin or the code — not fate.
How many heads should I expect in 100 flips?
50 on average, with a standard deviation of 5 — so 40–60 covers ~95% of sessions. Landing at 47 or 53 is silence; landing at 30 is a fairness investigation. The split-probability readout here prices your exact result on every flip.
Can I use this for decisions?
For low-stakes either/ors, absolutely — that’s what coins are for (the NFL ran on them for decades). For two-option choices with real weight, decide which option you’re hoping for while the coin is in the air; that information is the actual utility of the ritual.
Is this coin flip calculator free?
Yes — free, instant, no sign-up.