Free CRO Tools
Professional-grade calculators for A/B testers, CRO specialists, and growth teams. Calculate test duration, sample sizes, and statistical significance — all free, no signup required.
A/B Test Duration Calculator
Find out exactly how many days you need to run your A/B test to get statistically valid results. Avoid ending tests too early.
Calculate Duration →Sample Size Calculator
Calculate the minimum number of visitors per variation needed to detect a meaningful difference with your chosen confidence level and power.
Calculate Sample Size →Statistical Significance Calculator
Enter your control and variation results to instantly see if your A/B test has reached statistical significance, your p-value, and observed lift.
Test Significance →Why CRO Math Matters
Avoid False Positives
Ending a test early because results "look good" is one of the most common and costly CRO mistakes. Using proper sample sizes ensures your results are real — not just random noise.
Ship Winning Changes
Statistical significance tells you whether a difference is likely real or coincidental. Without it, you might ship changes that actively hurt conversions.
Plan Tests Properly
Knowing your required sample size before you start lets you plan test duration realistically, allocate traffic correctly, and avoid wasting weeks on underpowered experiments.
Credible Reporting
Share p-values and confidence levels with stakeholders to build trust in your CRO program. Data-driven decisions require data-driven evidence.
Want a Full CRO Audit?
These tools help you run better tests — but they can't tell you what to test. Our CRO audit identifies your highest-impact opportunities from real user data.
Book a CRO AuditStarting at $2,500 · 5–7 day delivery