Marketing

A/B Test Sample Size Calculator

Calculate required sample size per variant for a given baseline rate, minimum detectable effect, and confidence/power.

σ
statistics.power.calculator
A/B Sample Size
two-tailed95% confα=0.050β=0.20
> compute(n)
samples.per.arm
Required sample size per variant
31,234
total (A+B)
62,468
target rate
5.50%
duration
31.2d
// absolute lift = 0.50 pp · detect 10.0% relative improvement at 80% power
inputs.deck
drag or type
%
# current control conversion rate
%
# relative improvement you want to detect
v/d
# daily visitors to test surface
%
# % of traffic opted into the test
reference.tex
n =
[zα/2·√(2p̄q̄) + zβ·√(p₁q₁ + p₂q₂)]²
(p₂ − p₁)²
p₁ = 0.0500 baseline
p₂ = 0.0550 target
= 0.0525 pooled
zα/2 = 1.960
zβ = 0.842

Normal-approximation. Degrades at p<1% or tiny MDEs — treat result as a lower bound.