How this calculator works
The Celsius and Fahrenheit scales overlap in range but not in numbering: water freezes at 0 °C and 32 °F, and a span of 100 Celsius degrees equals a span of 180 Fahrenheit degrees, giving the exact factor 9/5. The conversion multiplies by 9/5 and then adds 32, and both constants are exact rationals.
Formula
°F = °C × 9/5 + 32.
Worked example
100 °C to Fahrenheit: 100 × 9/5 + 32 = 212 °F, the boiling point of water at sea level.
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Frequently asked questions
Where does the 9/5 come from?
A Celsius degree is 1.8 Fahrenheit degrees in size, and 1.8 is exactly 9/5. The 32 then realigns the two zero points.
Is there a quick mental estimate?
Double the Celsius value and add 30. It lands within a few degrees over everyday weather ranges, but use the exact formula when precision matters.
Can I convert a temperature below zero?
Yes. The formula handles negative values, and -40 °C gives exactly -40 °F.