A/B Test Sample Size Calculator

Enter your baseline conversion rate, minimum detectable effect, desired statistical power, and confidence level to compute the required visitors per variant.

Runs entirely in your browser. Nothing is uploaded.

How it works

STEP 1

Enter your baseline

Type in your current conversion rate (e.g. 5%) and the smallest relative change you want to detect.

STEP 2

Set significance & power

Choose your confidence level (1 − α) and statistical power (1 − β) from the dropdowns.

STEP 3

Get your sample size

Click Calculate. The tool shows visitors needed per variant and the total across both variants.