A/B Testing Tools & Guides

Statistical Calculators

A/B Test Sample Size Calculator

Calculate the exact number of visitors needed per variant before launching your A/B test. Enter your baseline conversion rate, minimum detectable effect, and desired power level. Includes common sample size tables, duration estimates, and guidance on choosing the right MDE for your business.

P-Value Calculator for A/B Tests

Compute p-values using the two-proportion Z-test and understand what they actually mean. Covers common significance thresholds (0.05, 0.01, 0.10), the five most common p-value misconceptions, and the difference between one-tailed and two-tailed tests.

Chi-Square Test Calculator

Apply the chi-square test of independence to A/B test data. Build contingency tables, compute degrees of freedom, and learn when to use chi-square versus the Z-test. Includes guidance on Yates' continuity correction and minimum sample size requirements.

Confidence Interval Calculator

Calculate confidence intervals for conversion rates using both the normal approximation and Wilson score method. Learn how to report A/B test results with confidence intervals and understand their relationship to statistical significance.

Bayesian Methods

Bayesian A/B Testing Guide

Comprehensive guide to Bayesian A/B testing using the Beta-Binomial conjugate prior model. Covers posterior probability calculation, expected loss as a decision metric, credible intervals, and when to choose Bayesian over frequentist methods.

Main Calculator

Use the ABWex A/B Test Significance Calculator for hands-on analysis with both frequentist and Bayesian modes, multi-variant comparison, revenue impact projections, and sample size planning — all in one tool.

About the Author

Built by Michael Lip — Solo developer with 10+ years experience. 140+ PRs merged into open source projects including Google Chrome and Axios. Creator of 20+ Chrome extensions and the Zovo developer tools collection.