Epidemiological RR to NNT Conversion Calculator

Convert relative risk (RR) and absolute risk reduction (ARR) to number needed to treat (NNT) or number needed to harm (NNH). Apply to baseline risk for clinical relevance.

 
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Physical Constants Reference
ConstantSymbolValue
Speed of lightc2.99792458×10⁸
Planck's constanth6.62607015×10⁻³‴
Boltzmann constant1.380649×10⁻²³
Avogadro's numberNₐ6.02214076×10²³
Gravitational constantG6.6743×10⁻¹¹
Gas constantR8.31446
Elementary chargee1.602176634×10⁻¹⁹
Electron massmₑ9.1093837015×10⁻³¹
Proton massmₚ1.67262192369×10⁻²⁷
Fine-structure constantα7.2973525693×10⁻³
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How to Use

Enter the values for the patient or scenario you are assessing. Convert relative risk (RR) and absolute risk reduction (ARR) to number needed to treat (NNT) or number needed to harm (NNH). Apply to baseline risk for clinical relevance. Use the rr to nnt result to inform your clinical assessment.

Frequently Asked Questions