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A/B test sample size calculator
This tool computes the sample size per variant from your baseline conversion rate, the lift you want to detect, your confidence level and your power.
A/B test sample size calculatorCalculator
Confidence level
Statistical power
Required sample
Per arm (control / variant)
53,148
visitors per variant
Total visitors needed
106,296
combined sample
Days to reach this sample
54 days
@ 2,000 visitors/day
This is arithmetic on your inputs. Your account will differ.
How this is calculated
This is the two-proportion sample size formula. It gives the visitors needed per variant for your baseline rate, the lift you want to detect, your confidence level and your power. It assumes a fixed sample size. The starting values are examples you change.
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