How to Calculate A/B Test

What is A/B Test?

A/B testing (split testing) compares two versions of a web page, email, or other element to determine which performs better. Statistical significance testing ensures the observed difference is not due to random chance. A result at 95% confidence means there is only a 5% probability the difference occurred by chance.

Formula

Calculate conversion rates for each variant: rate = conversions / visitors

Step-by-Step Guide

1Calculate conversion rates for each variant: rate = conversions / visitors
2Compute the pooled proportion: p_pool = (cA + cB) / (vA + vB)
3Calculate the standard error: SE = sqrt(p_pool × (1 − p_pool) × (1/nA + 1/nB))
4Z-score: z = (rateB − rateA) / SE
5If |z| ≥ 1.96, the result is significant at 95% confidence (two-tailed)

Worked Examples

Input

A: 1,000 visitors, 50 conversions. B: 1,000 visitors, 70 conversions

Result

Z = 2.08 — Significant at 96.2%

Relative lift: +40%. B is the winner.

Input

A: 200 visitors, 10 conversions. B: 200 visitors, 13 conversions

Result

Not significant — need more traffic

Small sample size means high uncertainty

Frequently Asked Questions

What is Ab Test Calc?

How accurate is the Ab Test Calc calculator?

The calculator uses the standard published formula for ab test calc. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Ab Test Calc calculator use?

This calculator works with inches, percentages. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Ab Test Calc calculator use?

The core formula is: Calculate conversion rates for each variant: rate = conversions / visitors. Each step in the calculation is shown so you can verify the result manually.

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