About the °f to °c calculation
Converting fahrenheit to celsius is not a simple multiplication, because the two scales start from different zero points. One degree Fahrenheit corresponds to -17.2222 celsius, but that ratio does not hold at other values — the formula below is what you actually need. The everyday scale in the United States, where water freezes at 32° and boils at 212°. The everyday temperature scale nearly everywhere, with 0 at the freezing point of water and 100 at its boiling point.
Formula
°C = (°F − 32) × 5/9
or equivalently: °C = (°F − 32) ÷ 1.8Worked example
To convert 98.6 °F: subtract 32 to get 66.6, then divide by 1.8. The answer is 37 °C.
Frequently asked questions
How many celsius are in a degree Fahrenheit?
One degree Fahrenheit equals -17.2222 celsius. Because these are temperature scales with different zero points, this is not a ratio you can multiply by — you have to apply the full formula for any other value.
How do I convert celsius back to fahrenheit?
Reverse the formula: undo the addition first, then the multiplication. One degree Celsius works out as 33.8 fahrenheit. Our Celsius to Fahrenheit page does it for you.
Is this conversion exact?
Yes. The Celsius, Fahrenheit and Kelvin scales are defined in terms of each other exactly, so the conversion carries no rounding error beyond what we display.
Is there anything that catches people out here?
Subtract 32 BEFORE dividing by 1.8, not after. Reversing the order is the single most common mistake in this conversion.
Sources
- NIST Special Publication 811 — Guide for the Use of the International System of Units