Sample size calculator

Alpha two-sided

/ =

Power

Sample size per group

Sample size in group 2

Allocation ratio n₁:n₂ :

Drop-out rate

Press the Calculate button to calculate the sample size.

Calculate
Sample size
Power (output decimal places: )

Advanced
Unequal sample sizes
Account for drop-outs
Bonferroni correction

Mean 1

Mean 2

Mean difference

Standard deviation

Standard deviation 2

Specific options
Unequal variances
Calculate mean difference from group means