TimelyScholarFree Tools › Convert r to d
Convert a correlation coefficient to Cohen's d, or Cohen's d to r, with an optional correction for unequal group sizes.
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| Cohen's d | 0.629medium by Cohen's benchmarks |
|---|---|
| r² | 0.090Share of variance explained |
| Formula | d = 2r / √(1 − r²)Equal group sizes |
r → d or d → r.
Add group sizes if they are unequal.
When one variable is group membership, the point-biserial correlation r and Cohen's d describe the same effect. For equal groups, d = 2r/√(1 − r²) and r = d/√(d² + 4).
Cohen's conventional benchmarks are 0.2, 0.5 and 0.8 for d, and 0.1, 0.3 and 0.5 for r (small, medium, large), but what counts as meaningful depends on the field.
Not exactly. With equal groups r = 0.3 corresponds to d ≈ 0.63; d = 0.5 corresponds to r ≈ 0.24.