Is the A/B Test Significance Calculator free to use?

Yes. The calculator is completely free with no account, sign-up, or subscription required.

Does the A/B Test Calculator store or upload my data?

No. All math runs locally in your browser. Visitor and conversion counts never leave your device.

What test does the calculator run?

It runs a two-tailed z-test for two proportions using a pooled standard error, with 95% Wald confidence intervals for each variant. The sample-size estimate uses 95% confidence and 80% power.

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A/B Test Significance Calculator

Enter visitor and conversion counts for both variants to calculate statistical significance, p-value, confidence level, and whether you have a clear winner.

Control (A)

Visitors

Conversions

Conversion Rate —

Variant (B)

Visitors

Conversions

Conversion Rate —

Confidence Level

—

90%

95%

Relative Uplift

—

B vs A conversion rate

Z-Score

—

Standard deviations from mean

P-Value (two-tailed)

—

Probability result is due to chance

95% Confidence Intervals

Control (A)

—

Variant (B)

—

Estimated Sample Size Needed (per variant)

—

To reach 95% confidence detecting the current observed uplift

How to use

Enter visitor and conversion counts for your control (A) — the original, unchanged baseline.
Enter visitor and conversion counts for your variant (B), then watch the confidence meter update live.
Wait until confidence reaches 95% (or your chosen threshold) before declaring a winner.

FAQ

A two-tailed z-test for two proportions with a pooled standard error, plus 95% Wald confidence intervals for each variant. The sample-size estimate targets 95% confidence at 80% power.

95% (p < 0.05) is the industry default. Use 99% for high-stakes changes like pricing or checkout. Decide your threshold before launching the test — never after seeing the results.

Usually no. 94% means a 6% chance the result is noise, above the standard threshold. Wait for more data unless traffic is severely limited and the business risk is low.