Absolute Risk Reduction Calculator
Use this free absolute risk reduction calculator to calculate absolute risk reduction, relative risk reduction and number needed to treat.
Health information notice: Results are estimates based on general formulas and may not reflect individual circumstances. This tool is not a diagnosis or substitute for personalized advice from a qualified healthcare professional.
How the absolute risk reduction calculator works
ARR = control event rate − treatment event rate. RRR = ARR ÷ control rate. NNT = 1 ÷ ARR.
Frequently asked questions
What is NNT?
The number of people who must be treated for one person to benefit. Lower numbers mean a stronger effect.
Results are estimates for general information only. They are not a substitute for professional advice where applicable. Found a mistake? Report an error.