basic

A/B Test Required Sample Size Calculator

n for comparing two proportions at given power and α.

Calculates the sample size per variant needed for an A/B test: n ≈ 2 × [z_α/2 + z_β]² × p̄(1−p̄) / (p₁−p₂)², using the pooled proportion method.

Priya Venkatesan By Priya Venkatesan
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see results.
Was this helpful?

How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

n = 2·(z_α/2 + z_β)²·p̄(1−p̄)/(p₁−p₂)²

In depth

Calculates the sample size per variant needed for an A/B test: n ≈ 2 × [z_α/2 + z_β]² × p̄(1−p̄) / (p₁−p₂)², using the pooled proportion method.