How does the Effect Size Calculator work?

Cohen's d = (μ1 - μ2) / σ (standardized mean difference) Then: d 0.8: large Then: Also: Pearson r for correlation, η² for ANOVA Then: Complements p-values (which depend on n).

Can you give an example of how to use the Effect Size Calculator?

Example: Input Mean diff 5, σ 2 gives a result of d=2.5.

Is the Effect Size Calculator free to use?

Yes — completely free with no registration, download, or subscription required. All calculations happen instantly in your browser.

How accurate is the Effect Size Calculator?

Our Effect Size Calculator uses verified mathematical formulas and is accurate to multiple decimal places. Results are calculated in real-time using the same methods used by professionals.

Mathematics

Effect Size Calculator

Effect Size (Cohen's d, Hedges\' g)

Mean 1

Mean 2

SD 1

SD 2

Calculates effect size (magnitude of effect) independent of sample size.

Symbol	Name	Unit	Description
d	(μ1 - μ2) / σ (standardized mean difference)	—	(μ1 - μ2) / σ (standardized mean difference)

Difficulty:intermediate

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Did You Know?

Large sample with d = 0.1 (tiny effect) may be significant but practically meaningless.

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Effect Size Calculator

Effect Size (Cohen's d, Hedges\' g)

What is Effect Size Calculator?

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Effect Size (Cohen's d, Hedges\' g)