Free Tool
A/B Test Duration Calculator
Find out exactly how long to run your A/B test based on your traffic and goals. Stop guessing, start knowing.
1 Enter Your Parameters
Average daily visitors to the page you're testing
%
Your current conversion rate on this page
%
Smallest improvement you want to detect (e.g., 20% = 5% → 6.00%)
Advanced Settings
Common Mistakes
- • Stopping when you first see statistical significance
- • Running tests for less than 7 days
- • Ignoring day-of-week and seasonal effects
Best Practices
- • Always run for at least 1-2 full weeks
- • Set your duration before starting the test
- • Don't peek at results until the test is complete
Duration Reference Table
Quick reference based on 5% baseline conversion (95% confidence, 80% power)
| Daily Traffic | Weekly | 20% MDE | 30% MDE | 50% MDE |
|---|---|---|---|---|
| 500 | 3,500 | ~3 weeks | ~2 weeks | ~1 week |
| 1,000 | 7,000 | ~2 weeks | ~1 week | ~1 week |
| 5,000 | 35,000 | ~1 week | ~1 week | ~1 week |
| 10,000 | 70,000 | ~1 week | ~1 week | ~1 week |
| 50,000 | 350,000 | ~1 week | ~1 week | ~1 week |