Calculate the
Sample Size
It's simple: fill the fields and click on the ⚡️ button.

Pre-test analysis

The Sample Size Calculator is your go-to tool for doing pre-test analysis (power analysis).

How many visitors does your test require? What type of test is best to use with your current traffic levels?

Once you fill in the required information, it will calculate the sample size needed for your test to reach the desired statistical power and confidence level and hence avoid underpowered experiments.

Everything is designed to be as intuitive as possible, but if you find yourself in need of guidance, hover over tooltips or click on the help icons to access detailed information.

Inputs
Confidence Level:
70%
75%
80%
85%
90%
95%
99%
Power Level:
70%
75%
80%
85%
90%
95%
99%
Margin of error:
1%
5%
10%
15%
20%
25%
30%
Testing for:
Superiority
Superiority or Inferiority
Non-inferiority
Before and After
Survey
Metric Type:
Conversion Rate
Average
Population Size
Parameters
Baseline Average
The value of success metric you aim to improve
Standard Deviation
Measure of the amount of variation in a set of values
Minimum Effect - Relative
Expressed as a percentage of the baseline metric
Minimum Effect - Absolute
Estimate it
Expressed as absolute value of the baseline metric
Number of Variants
Not counting control
Traffic
Number of uniques
Number of Success Metrics
Number of Guardrail Metrics
Margin
Expressed as a percentage of the baseline metric
Not Worse
Variant metric to be not worse than:
Not Worse
Variant metric to be not worse than:
OFF
Plots
Inputs
Recap Cards
Confidence Level
1-α
Margin of Error
for the study
Population Size
of the study
Minimum Sample Size
for the study
Recap Cards
Confidence Level
1-α
Power Level
1-β
Total Variants
Including Control
Baseline
Metric
Minimum Effect
Traffic
Samples
Each group
Total Samples
Required for the test
Duration
Estimate of days
Sample size in relation to power
Sample size in relation to minimum effect