How to Calculate Heat Index Calc
What is Heat Index Calc?
The heat index (also called apparent temperature or feels-like temperature in summer) estimates how hot it actually feels based on air temperature and relative humidity. High humidity prevents sweat from evaporating effectively, reducing the body's ability to cool itself. The Rothfusz (1990) regression equation used by NOAA and the NWS is the most widely accepted formula.
Formula
- HI
- −42 — −42
Step-by-Step Guide
- 1Based on Rothfusz (1990) regression of physiological studies
- 2HI = −42.379 + 2.04901523T + 10.14333127R − 0.22475541TR ...
- 3T = air temperature (°F), R = relative humidity (%)
- 4Applies when T ≥ 80°F (27°C) and RH ≥ 40%
- 5Accuracy: ±1.3°F under typical conditions
Worked Examples
Frequently Asked Questions
What is Heat Index Calc?
The heat index (also called apparent temperature or feels-like temperature in summer) estimates how hot it actually feels based on air temperature and relative humidity. High humidity prevents sweat from evaporating effectively, reducing the body's ability to cool itself
How accurate is the Heat Index Calc calculator?
The calculator uses the standard published formula for heat index calc. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.
What units does the Heat Index Calc calculator use?
This calculator works with inches, Celsius, Fahrenheit, percentages. You can enter values in the units shown — the calculator handles all conversions internally.
What formula does the Heat Index Calc calculator use?
The core formula is: HI = −42.379 + 2.04901523T + 10.14333127R − 0.22475541TR . Each step in the calculation is shown so you can verify the result manually.