Calculate NNH = 1 / ARI (absolute risk increase) for adverse effects of an intervention. Compare NNT vs NNH to compute the likelihood of being helped vs harmed (LHH ratio).
| Constant | Symbol | Value |
|---|---|---|
| Speed of light | c | 2.99792458×10⁸ |
| Planck's constant | h | 6.62607015×10⁻³‴ |
| Boltzmann constant | kʙ | 1.380649×10⁻²³ |
| Avogadro's number | Nₐ | 6.02214076×10²³ |
| Gravitational constant | G | 6.6743×10⁻¹¹ |
| Gas constant | R | 8.31446 |
| Elementary charge | e | 1.602176634×10⁻¹⁹ |
| Electron mass | mₑ | 9.1093837015×10⁻³¹ |
| Proton mass | mₚ | 1.67262192369×10⁻²⁷ |
| Fine-structure constant | α | 7.2973525693×10⁻³ |
Enter the values for the patient or scenario you are assessing. Calculate NNH = 1 / ARI (absolute risk increase) for adverse effects of an intervention. Compare NNT vs NNH to compute the likelihood of being helped vs harmed (LHH ratio). Use the nnh calculator result to inform your clinical assessment.