Heat Index Calculator
Use this heat index calculator entirely in your browser.
Most meaningful in hot, humid conditions.
Calculations happen locally in your browser.
How to use this calculator
- Enter the labelled values and review the live result.
- Review the live result and use Copy result when you need to share it.
How the calculation works
The Rothfusz regression combines Fahrenheit temperature and relative humidity, then converts back to Celsius.
Formula
The Rothfusz regression combines Fahrenheit temperature and relative humidity, then converts back to Celsius.
Step-by-step calculation
- Enter the labelled values and review the live result.
- The Rothfusz regression combines Fahrenheit temperature and relative humidity, then converts back to Celsius.
- Check the displayed result, then copy it if needed.
Worked example
32°C at 65% humidity produces a higher apparent temperature.
Risk guidance
Frequently asked questions
Does this tool send my inputs anywhere?
No. The interactive calculation runs in your browser and this site does not submit tool inputs to a backend.
How should I use the result?
Check that the entered units and values match your situation, especially around dates, breaks, and rounding.
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