About the Minimum Detectable Effect Calculator
The smallest relative lift an A/B test can reliably detect for your baseline rate, traffic, significance and power.
Also known as: mde calculator, detectable lift, ab test power, statistical power calculator.
How to use this calculator
- Enter baseline conversion rate, visitors per variant, significance, power.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
MDE ≈ (z₁₋α/₂ + z₁₋β)·√(2p(1 − p)/n)
Worked example
Using the values pre-filled in the calculator above:
- Baseline conversion rate = 4 %
- Visitors per variant = 10,000
- Significance: 95%
- Power: 80%
the calculator returns:
- Minimum detectable effect (relative): 19.41%
- Absolute difference: 0.7764%
- Detectable variant rate: 4.7764%