How to Use the NNT Calculator
Enter the experimental and control event rates. You may use decimals such as 0.08 or percentage-style numbers such as 8 for 8%; values above 1 are interpreted as percents.
If the experimental event rate is lower, the result is NNT. If it is higher, the result is NNH. Equal rates cannot produce a finite result because the absolute risk difference is zero.
Formula and Method - NNT Calculator
NNT = 1 ÷ |control event rate - experimental event rate|NNT is based on absolute risk difference, not relative risk. A larger absolute difference produces a smaller NNT; a difference close to zero produces a very large NNT.
Use Cases for the NNT Calculator
- Converting trial event rates into a patient-centered treatment benefit measure.
- Comparing interventions by absolute benefit rather than relative effect alone.
- Explaining how many people must receive treatment to prevent one event.