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Updated 2026-03-07 UTC
Hedges’ g Calculator — Small‑Sample Corrected Cohen’s d — GetCalcMaster
Compute Hedges’ g from Cohen’s d using the small‑sample correction J(df). Useful for meta-analysis and small studies.
Hedges’ g is Cohen’s d with a small‑sample correction. For small df, g is slightly smaller (less biased) than d.
Important: Educational. For specialized designs (paired, clustered), use an effect size formula matched to the design.
What this calculator is
The Statistics Calculator is an interactive tool inside GetCalcMaster. It’s designed to help you explore scenarios, understand formulas, and document assumptions.
Key features
- Clear relationship to Cohen’s d (g = J·d)
- Uses df = n1 + n2 − 2 for two independent groups
- Approaches d as sample sizes grow
Formula
df = n1 + n2 - 2
J(df) ≈ 1 - 3/(4df - 1)
g = J(df) * dQuick examples
If df is large (say 100+), J(df) is very close to 1 → g ≈ d.If df is small, g will be slightly smaller than d (bias correction).
Verification tips
- J(df) should be less than 1 and approach 1 as df increases.
- g keeps the sign of d (direction preserved).
Common mistakes
- Using the wrong df (e.g., n−1 instead of n1+n2−2 for two groups).
- Applying the correction twice (don’t compute d from g and then re-correct).
How to use it (quick steps)
- Compute Cohen’s d for your two groups.
- Compute df = n1 + n2 − 2.
- Compute the correction J(df).
- Multiply: g = J(df) · d.
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FAQ
Is this calculator official?
No. GetCalcMaster provides educational estimates and learning tools. Always verify against official definitions, documents, or professional advice.
Do you store my inputs on the server?
No. Calculations run locally in your browser. Optional remember/restore features (if enabled) use local browser storage.
Tip: For reproducible work, save your inputs and reasoning in Notebook.