How to Use the Ad Copy A/B Test Duration Calculator
Before testing a new ad copy variant, knowing how long it needs to run for reliable results helps you plan budget and timeline efficiently. This calculator computes the statistically required click sample size, then divides it by your daily clicks to get the minimum test duration.
The minimum detectable effect (MDE) is the smallest conversion-rate improvement you consider meaningful. A lower MDE requires detecting a finer difference, which increases the required click volume and duration. Copy tests usually aim for larger differences, so setting MDE around 10-20% is realistic.
Ads with low average daily clicks can produce long durations. In that case, increase budget to drive more impressions and clicks, or raise the MDE to shorten the test — and stick to the full planned duration to keep results trustworthy.
Frequently Asked Questions
It uses ad clicks instead of page visitors as the base metric. Ad copy tests typically compare click-through rate itself or post-click conversion, but the duration calculation follows the same statistical principle.
You can increase your budget to drive more impressions and clicks, or raise the MDE to lower the required sample size. If the duration is still too long, lowering confidence to 90% can also balance statistical power against duration.