Tools

Free sample-size calculators — no login, no installs. Pick a study design and get a defensible estimate with a copy-ready methods paragraph.

Sample size: diagnostic test (sensitivity & specificity)

sample size

diagnostic

sensitivity

specificity

Sample-size calculator for a diagnostic-accuracy study (Buderer 1996). Computes the number of diseased and non-diseased participants needed to estimate sensitivity and specificity with a target precision.

May 8, 2026

Sample size: logistic regression

sample size

logistic regression

modelling

Sample-size calculator for logistic regression — events-per-variable rule plus the Hsieh (1989) formula. Plain-language inputs and a copy-ready methods paragraph.

May 8, 2026

Sample size: comparing two means

sample size

means

t-test

Fast, MMed-friendly sample-size calculator for comparing two independent means (two-sample t-test). Plain-language inputs, citations, and a copy-ready methods paragraph.

May 8, 2026

Sample size: estimating a single prevalence

sample size

prevalence

survey

Sample-size calculator for estimating a single proportion or prevalence with a desired margin of error. Includes design effect and finite-population correction.

May 8, 2026

Sample size: comparing two proportions

sample size

proportions

rates

Fast, MMed-friendly sample-size calculator for comparing two independent proportions or rates. Plain-language inputs, citations to support each assumption, and a copy-ready methods paragraph.

May 7, 2026