Effect Size Calculator for T-Test

For a two-sample independent t-test, an effect size measures the magnitude of the difference between the two sample means.

This calculator finds three different effect size measures: Cohen’s d, Glass’s delta, and Hedges g.

Cohen’s d: the appropriate effect size measure if the two samples have similar standard deviations and the same sample size.

Glass’s delta: the appropriate effect size measure if you want to measure the effect size using the first sample standard deviation as the control group and each sample has a different standard deviation.

Hedges’ g: the appropriate effect size measure if the two samples have different sample sizes.

To find these three effect size measures, enter the appropriate numbers in the table below for the two samples and click the “Calculate” button.

Group 1 Group 2
Sample mean (x)
Sample standard deviation (s)
Sample size (n)

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