Minimum Detectable Lift Calculator
Enter your traffic and timeline to see the smallest change your test could reliably detect, so you know if it's worth running.
How the calculator works
It answers the Sample Size Calculator's question in reverse, using the same formula. Instead of choosing a lift and finding the visitors you need, you enter your visitors and find the lift they can detect.
The result is relative, so a 20% lift on a 5% conversion rate means reaching 6%. Testing more variants splits your traffic and raises the smallest lift you can detect.
How to use the result
Compare the result with the change you realistically expect. If you can only detect a 30% lift and your idea might bring 5%, the test will probably end with no clear answer.
When the number is too high, run the test longer, use a page with more traffic, or test a bolder change. Lower-traffic sites often do better testing fewer, larger ideas.
Disclaimer
This tool is for informational purposes only, and we don't guarantee the accuracy of its results. You're responsible for verifying any results before relying on them. See our terms of use.
Common questions
Is my information saved?
No. Your numbers stay in your browser, and they aren't sent to anyone.
What does minimum detectable lift mean?
It's the smallest relative change a test can reliably pick up at your chosen confidence and power. Smaller real changes can still happen, but the test probably won't confirm them.
Do I need to choose a sample size instead?
Use this calculator when your traffic is fixed, and use the Sample Size Calculator when you know the lift you care about.
Try the Sample Size CalculatorWant help putting this to work?
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