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.