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Cohen's d Effect Size Calculator

Calculate Cohen's d — the standardized difference between two group means in pooled standard deviation units. Measures how big an effect is, not just whether it is significant.

Group 1 Mean

Group 2 Mean

Group 1 Standard Deviation

Group 2 Standard Deviation

Statistics

Standard Deviation Calculator

Compute the sample standard deviation directly from three summary statistics — sample size n, the sum of values Σx, and the sum of squared values Σx². This is the spread metric used in virtually every empirical study, quality-control chart, and risk model.

Sample Size

Sum of Values

Sum of Squares

Key differences

	Cohen's d Effect Size Calculator	Standard Deviation Calculator
Category	Statistics	Statistics
Inputs required	4	3
Result	Cohen's d	Standard Deviation
What it does	Calculate Cohen's d — the standardized difference between two group means in pooled standard deviation units. Measures how big an effect is, not just whether it is significant.	Compute the sample standard deviation directly from three summary statistics — sample size n, the sum of values Σx, and the sum of squared values Σx². This is the spread metric used in virtually every empirical study, quality-control chart, and risk model.