NNT / NNH Calculator

Convert effect measures to Number Needed to Treat or Harm

Clinical Decision Making

Input Parameters

Enter effect measure and baseline risk

Effect Measure Type

Risk Ratio Value

Values < 1 indicate benefit, > 1 indicate harm

Lower 95% CI

Upper 95% CI

Baseline Risk (Control Event Rate)

Probability of outcome in untreated/control group

Enter parameters and click calculate to see results

Formulas

NNT = 1 / ARR

ARR = CER - EER (Control - Experimental Event Rate)

From RR: ARR = CER × (1 - RR)