Calculator · deterministic

Sample size calculators

Pick by design: every calculation runs deterministically on the server. The hypothesis-test calculators are validated against G*Power and R pwr, the survey calculator against an independent implementation (statsmodels) and published examples. Free; no sign-up.

Surveys and prevalence (single-proportion estimate)

Survey sample size calculator (Cochran, Yamane)Estimating a percentage within a margin of error: the sample a survey or prevalence study needs, with finite population, design effect and response rate.

Comparing means

Two-sample t-test sample size calculatorComparing the means of two independent groups: participants per arm from Cohen's d, α and power.Paired t-test sample size calculatorBefore–after in the same person, or two methods on the same subjects: complete records from dz.One-way ANOVA sample size calculatorThree or more independent groups: total sample from Cohen's f and the number of groups.Mann-Whitney U test sample size calculatorSkewed outcome or small sample: n for the non-parametric two-group comparison.Non-inferiority sample size calculator (means)Showing the new method is not meaningfully worse: per-arm n from the margin and the SD.

Comparing rates

Sample size calculator for comparing two proportionsComparing complication, success or response rates between two groups: per-arm n from p₁ and p₂.

Diagnostic accuracy

Sensitivity / specificity sample size calculatorEstimating a diagnostic test's accuracy with a confidence interval: diseased cases from the expected value and CI half-width.Sample size: sensitivity above a thresholdShowing a test's sensitivity exceeds a clinical threshold: cases from the expected value and the threshold.McNemar sample size calculator (paired tests)Comparing two diagnostic tests on the same patients: cases from the discordant-pair rates.

Comparison

G*Power alternativeHow it differs from G*Power, when each fits better, and a check against three published examples.

To choose the expected value from the literature, test your idea on KONSİL. For the concepts, see the effect size and sample size adjustments guides.