Does this assume a 50/50 split?
Yes. The calculator sizes a classic A/B test with equal traffic per variant. If you plan an uneven allocation, adjust the per-variant totals accordingly.
Step-by-step walkthrough
A/B Test Sample Size Calculator Guide
Use this companion guide beside the interactive calculator to make sure you understand the “why” behind every click. Each section includes the classroom explanation, student-friendly language, and quick practice prompts.
Before you start
Collect the data points listed below and double-check their units. Keeping an organized “givens” list is one of the fastest ways to reduce math errors and impress exam graders.
- ab testing
- sample size
- power analysis
- minimum detectable effect
Detailed procedure
Step 1
Enter your current conversion rate (control) and the absolute lift you want to be able to detect.
Step 2
Choose a confidence level (alpha) and statistical power (1 − beta).
Step 3
Optional: provide daily visitors to estimate how long the test will need to gather that many samples.
Teaching & troubleshooting tips
Why does the sample size explode for tiny lifts?
Detecting minuscule changes demands a very small denominator (p₂ − p₁). When the effect size shrinks, the required sample grows quadratically—plan for more time or accept a larger detectable lift.