Compare calculators

Both calculators run independently — change the inputs on either side to compare results.

Number Needed to Treat (NNT) Calculator

Calculate the number of patients who must be treated to prevent one additional bad outcome, from the control and treatment event rates. A key measure of clinical effectiveness.

Control Group Event Rate (%)

Treatment Group Event Rate (%)

Probability

Sample Size Calculator

Determine the minimum sample size needed for a survey or experiment given your confidence level, margin of error, and population size. Prevents under-powered studies and over-budgeted data collection.

Population Size (N) (people)

Confidence Level

Margin of Error (%)

Response Distribution

Key differences

	Number Needed to Treat (NNT) Calculator	Sample Size Calculator
Category	Statistics	Probability
Inputs required	2	4
Result	Number Needed to Treat (patients)	Required Sample Size (samples)
What it does	Calculate the number of patients who must be treated to prevent one additional bad outcome, from the control and treatment event rates. A key measure of clinical effectiveness.	Determine the minimum sample size needed for a survey or experiment given your confidence level, margin of error, and population size. Prevents under-powered studies and over-budgeted data collection.