Sample Size Calculator
Sample sizes for prevalence studies, means, proportions, case-control, cohort studies and RCTs.
Research & Academic Tools
27 free tools
Free research tools for students, academics and systematic reviewers: sample size, odds ratios, diagnostic accuracy, effect sizes, meta-analysis helpers, PRISMA diagrams, DOI and citation tools, and data screening.
All 27 research & academic tools
Odds Ratio Calculator
Odds ratio with confidence interval, z-test and Fisher's exact p from a 2×2 table.
Relative Risk Calculator
Relative risk, risk difference, ARR, RRR and NNT with confidence intervals.
Diagnostic Accuracy Calculator
Sensitivity, specificity, PPV, NPV, likelihood ratios and diagnostic odds ratio with CIs.
NNT / NNH Calculator
Number needed to treat or harm, with absolute and relative risk reduction.
2×2 Contingency Table Calculator
Chi-square, Fisher's exact test, odds ratio, relative risk and attributable risk.
Mean, SD & SEM Calculator
Mean, standard deviation, standard error, median, quartiles and CI from raw data.
Confidence Interval Calculator
Confidence intervals for means, proportions, differences, odds ratios and relative risks.
P-value Calculator
Convert z, t, chi-square, F and r statistics into p-values.
Effect Size Calculator
Cohen's d, Hedges' g, Glass's Δ, r, eta-squared and effect size conversions.
Statistical Power Calculator
Power or required sample size for t-tests, proportions and correlations.
SD, SE & CI Converter
Convert between standard deviation, standard error and confidence interval.
Meta-analysis Effect Converter
Convert ratios, log effects, CIs, p-values, medians and SMDs for meta-analysis.
I² Heterogeneity Calculator
Cochran's Q, I², H², τ² and pooled estimates for a meta-analysis.
Leave-One-Out Meta-analysis
Re-pool a meta-analysis leaving out each study in turn to test robustness.
PRISMA Flow Diagram Generator
Create a PRISMA 2020 flow diagram and export it as SVG, PNG or PDF.
Reference Formatter (DOI to Citation)
Turn DOIs into APA, Vancouver, AMA, Harvard, Chicago, IEEE and MLA references.
Vancouver Reference Generator
Build Vancouver-style references for journals, books, chapters and websites.
DOI Extractor
Extract, clean and deduplicate DOIs from reference lists and flag malformed ones.
PMID Extractor
Extract PubMed IDs from text and links, remove duplicates and open them in PubMed.
Reference Duplicate Finder
Find duplicate references by DOI, PMID, exact and near-identical titles.
Journal Abbreviation Finder
Look up NLM and ISO journal title abbreviations, and expand abbreviations.
Citation Number Checker
Check numbered citations for gaps, order, ranges and uncited references.
CSV Descriptive Statistics
Summary statistics for every column in a CSV file: N, missing, mean, SD and more.
Missing Data Checker
Count and chart missing values per variable and find incomplete rows in a dataset.
Outlier Detector
Flag outliers with the IQR rule, z-scores or modified z-scores without deleting data.
Normality Checker
Shapiro–Wilk test, skewness, kurtosis, histogram and Q–Q plot for your data.
Practical guides
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How to Use Sample Size Calculator
Calculate sample size for prevalence surveys, means, two proportions, case-control, cohort studies and RCTs, with power, dropout and design effect.
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How to Use Odds Ratio Calculator
Calculate the odds ratio from a 2×2 table with Woolf confidence interval, z-test and Fisher’s exact p-value, for case-control studies and more.
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How to Use Relative Risk Calculator
Calculate relative risk, risk difference, absolute and relative risk reduction and NNT with confidence intervals from cohort or trial 2×2 data.
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How to Use Diagnostic Accuracy Calculator
Calculate sensitivity, specificity, PPV, NPV, likelihood ratios, accuracy, Youden index and diagnostic odds ratio with 95% CIs from a 2×2 table.
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How to Use NNT / NNH Calculator
Calculate the number needed to treat or harm, absolute and relative risk reduction, from event counts or rates, with Altman’s confidence interval.
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How to Use 2×2 Contingency Table Calculator
Analyse a 2×2 table with Pearson and Yates chi-square, Fisher’s exact test, odds ratio, relative risk, risk difference and expected counts.
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