Krippendorff's Alpha Calculator
Measure inter-coder reliability for content analysis. Paste one row per unit with the category code each coder assigned.
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Krippendorff's alpha
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Enter valid values to see your result. Use the field hints or open the data guide for help.
Calculate it yourself
For two coders and four items, use the numeric category pairs 1,1; 1,2; 2,2; and 2,2.
Follow this worked example, then repeat the steps with your own numbers.
Build the coincidence counts
The coincidence table has rows 2,1 and 1,4. Its category totals are n₁ = 3 and n₂ = 5; n = 8.Count both ordered coder pairs for each item. For an item with m available ratings, give each ordered pair weight 1/(m − 1); ignore items with fewer than two ratings.
Calculate observed disagreement
Dₒ = off-diagonal total ÷ n = (1 + 1) ÷ 8 = 0.25.Calculate expected disagreement
Dₑ = [2 × n₁ × n₂] ÷ [n(n − 1)] = (2 × 3 × 5) ÷ (8 × 7) = 30/56.Compare observed and expected disagreement
α = 1 − Dₒ/Dₑ = 1 − 0.25/(30/56) ≈ 0.533.With more than two categories, sum nᶜ × nᵈ over every ordered pair of different categories in the expected-disagreement numerator.
This is nominal alpha: all disagreements count equally. Missing ratings are allowed, but an item needs at least two available ratings to contribute.
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Collect coder ratings by subject and bring the exported category matrix into this calculator for nominal alpha.
Why Krippendorff’s alpha
Krippendorff’s alpha is the standard reliability measure for content analysis and coding studies. Unlike percent agreement it corrects for chance, and it handles any number of coders as well as missing values, so coders do not all have to rate every unit. This calculator uses the nominal difference function, which treats every pair of different codes as equally far apart.
How to read the value
Alpha ranges up to 1. The common threshold is 0.80: data at or above it are considered reliable. Values from 0.667 up to 0.80 are only tentatively acceptable, suitable for drawing cautious conclusions, and anything below 0.667 is usually treated as too unreliable to use.
Frequently asked questions
Can rows have different lengths?
Yes. If a coder did not rate a particular unit, simply leave that value out of the row. Krippendorff’s alpha is designed to handle missing ratings.
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