By ToolzHive
About this tool
Cohen's d, Hedges' g, Glass's Δ, r, eta-squared and effect size conversions.
How to use Effect Size Calculator
- Choose what you have: group means and SDs, a t or F statistic, r, chi-square or an odds ratio.
- Enter the figures and sample sizes.
- Read the effect size, its interval and equivalent measures.
Worked example
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.
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.
Put this guide into practice
- Effect Size Calculator — Cohen's d, Hedges' g, Glass's Δ, r, eta-squared and effect size conversions.