NexSample: Sample Size Calc

NexSample is a free sample size calculator for clinical research, designed for medical residents, fellows, postgraduate students, and researchers. It includes 26 calculators covering the most common study designs in clinical trials, observational research, and diagnostic studies–plus calculators for agreement, reliability, and regression that are hard to find elsewhere. Whether you are planning a thesis, protocol, dissertation, grant proposal, or manuscript, NexSample helps you calculate sample size quickly and accurately, with full formulas and references shown for every calculation. 26 calculators in one app RCT (parallel) / cohort (unmatched) • Two independent means • Two proportions • One-way ANOVA (≥3 groups) • Survival / time-to-event analysis RCT (cross-over) / cohort (matched) • Paired means • Paired proportions Non-inferiority / equivalence • Two means • Two proportions Case-control • Unmatched • Matched Cross-sectional • Prevalence comparison Descriptive • Single proportion • Single mean Diagnostic studies • Sensitivity / specificity • Compare sensitivity / specificity of two tests • AUC estimation • Likelihood ratios Agreement studies • Cohen’s kappa • Intraclass correlation coefficient (ICC) • Bland–Altman method comparison Regression / association • Correlation coefficient • Multiple linear regression • Logistic regression • Cohen’s w Advanced • Cluster randomized trial Verified formulas Each calculator has been checked against published worked examples and standard biostatistics references. Worked examples Every calculator includes an example that can be viewed with a single tap, helping users understand the required inputs and the expected output. Contextual help Built-in field-level guidance explains what to enter, including units, ranges, and interpretation. Write-up generator Generate a ready-to-paste sample size justification paragraph for your proposal, protocol, thesis, or manuscript. Dropout adjustment Use the dropout slider to adjust for anticipated attrition and see updated sample sizes instantly. Designed for researchers • Clean, distraction-free interface • Works offline • No ads, no tracking, no account required • Formula and reference shown for every calculation NexSample is designed to be a practical sample size calculator for researchers in clinical research, epidemiology, and medical education. Conceived and developed by M Jeeva Sankar, drawing on years of experience in clinical research, teaching, and mentoring. A JAmR initiative by M Jeeva Sankar and Ameya Sankar.