Number Needed to Treat Calculator
Calculate absolute risk reduction and number needed to treat. This free tool is designed for quick academic, research, laboratory or everyday calculations while keeping the underlying method visible.
Formula or method
NNT = 1 / |control risk − treatment risk|.
How to use it
Enter the requested values, run the calculation and review the result together with the interpretation shown by the tool. Check units and assumptions before using the output in formal work.
Important note
Results may be affected by rounding, input quality and context-specific rules. For high-stakes scientific, clinical or academic decisions, verify the calculation against the applicable official method or guidance.
Frequently asked questions
What does this tool calculate?
Calculate absolute risk reduction and number needed to treat.
Can I use the result in formal work?
Use the result as a calculation aid and verify assumptions, units and any field-specific rules before formal use.