Free · Everyday · Weather

Heat Index Calculator

Estimate apparent temperature from air temperature and relative humidity with the NOAA regression.

  • Checked formula
  • Private in your browser
  • No signup
Calculator inputs

Enter your values

Result

Your calculation

Heat index
38.7 °C
Apparent increase
6.7 °C

This shaded, light-wind estimate is most meaningful in hot, humid conditions. Direct sun can increase heat stress.

How to use this calculator

  1. Enter the values and choose the units that match your situation.
  2. Calculate to see the primary answer and useful conversions.
  3. Review the assumptions before using the result for a project or decision.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.