Free statistical calculators

Sample size for Comparison of means

Input
Type I error - Alpha:
Type II error - Beta:

Difference:
Standard deviation group 1:
Standard deviation group 2:
Ratio of sample sizes in Group 1 / Group 2:
Result
Number of cases required in group 1:
Number of cases required in group 2:
Total sample size (2 groups together):

For details, see the MedCalc manual: Sample size: Comparison of two means.

MedCalc Software Ltd. Sample size for Comparison of means. https://www.medcalc.org/en/calc/sample-size-comparison-of-means.php (Version 23.4; accessed November 7, 2025)