Free statistical calculators

Sample size for a Confidence interval of a difference between means

Confidence interval
Confidence Interval (%):
Input
Pooled standard deviation:
Confidence interval width (2-sided):
Ratio of sample sizes in Group 1 / Group 2:
Results
Number of cases required in group 1:
Number of cases required in group 2:
Total sample size (2 groups together):

MedCalc Software Ltd. Sample size for a Confidence interval of a difference between means. https://www.medcalc.org/en/calc/sample-size-ci-difference-between-means.php (Version 23.4.5; accessed January 14, 2026)