Fisher Exact2×2 Test Calculator
Compute a bounded fixed-margin Fisher exact probability with a named one- or two-sided alternative.
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How to use Fisher Exact2×2 Test Calculator
With the margins fixed, each possible top-left count has exact integer weight C(row1,k)C(row2,col1−k). One-sided tails compare k; two-sided probability ordering sums weights no larger than the observed weight, using exact comparisons.
- Enter json2×2 count table.
- Choose the stated convention and check the units and supported model.
- Calculate, inspect the result, then copy or download it.
Good to know
- 2×2 nonnegative whole counts, grand total1–500. Degenerate zero margins withhold inference. Conditional fixed-margin test only; no mid-p, randomized test, causal or clinical conclusion.
- Runs locally. Text/JSON fields are capped at30,000 characters; stricter page-specific and numeric-string limits also apply. Numeric inputs are bounded to magnitude1e15 and nonzero magnitude at least1e-100 unless an exact-string mode states otherwise. Approximate summaries use12 significant digits; CSV numeric cells retain the complete stored value and potentially formula-like string cells gain a protective apostrophe; unsupported, non-finite or detected underflow states return an error.
Common questions
Why does the two-sided definition matter?
Discrete tables admit several conventions. This tool explicitly uses probability ordering, not double the smaller tail or mid-p.
Is the input uploaded or saved?
No. The tool calculates inside this browser tab and provides a local download; it does not persist your input.
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