Effect Size Calculator
Cohen's d, Hedges' g, Glass's Δ, r, eta-squared and effect size conversions.
Enter your values to see the result.
Hedges' g applies the small-sample correction J = 1 − 3 ÷ (4(n₁ + n₂) − 9). Odds ratio conversions use Chinn's (2000) logistic approximation d = ln(OR) × √3 ÷ π. Results use standard large-sample formulas and are meant to support, not replace, a statistician's review. Check the assumptions behind each method before you report the numbers.
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- Meta-analysis Effect Converter — Convert effects and their SEs for meta-analysis.
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How to use the Effect Size Calculator
Cohen's d, Hedges' g, Glass's Δ, r, eta-squared and effect size conversions.
- 1 Choose what you have: group means and SDs, a t or F statistic, r, chi-square or an odds ratio.
- 2 Enter the figures and sample sizes.
- 3 Read the effect size, its interval and equivalent measures.
Example and practical tips
Means of 24.5 (SD 5.2) and 21.0 (SD 4.8) with 30 per group give Cohen’s d = 0.70 and Hedges’ g = 0.69, a medium effect.
Frequently asked questions
What is the difference between d and g?
Hedges’ g applies a small-sample correction to Cohen’s d. It is preferred in meta-analysis, especially with fewer than 20 per group.
What counts as a large effect?
Cohen’s rough guide is 0.2 small, 0.5 medium and 0.8 large, but what matters depends on your field.
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