About the °c to °f calculation
Converting celsius to fahrenheit is not a simple multiplication, because the two scales start from different zero points. One degree Celsius corresponds to 33.8 fahrenheit, but that ratio does not hold at other values — the formula below is what you actually need. The everyday temperature scale nearly everywhere, with 0 at the freezing point of water and 100 at its boiling point. The everyday scale in the United States, where water freezes at 32° and boils at 212°.
Formula
°F = (°C × 9/5) + 32
or equivalently: °F = (°C × 1.8) + 32Worked example
To convert 25 °C: multiply by 1.8 to get 45, then add 32. The answer is 77 °F.
Frequently asked questions
How many fahrenheit are in a degree Celsius?
One degree Celsius equals 33.8 fahrenheit. 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 fahrenheit back to celsius?
Reverse the formula: undo the addition first, then the multiplication. One degree Fahrenheit works out as -17.2222 celsius. Our Fahrenheit to Celsius 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?
Temperature is the one conversion that is not a simple multiplication. The scales have different zero points, so you must multiply by 9/5 AND add 32 — doing only one gives an answer that is wrong by tens of degrees.
Sources
- NIST Special Publication 811 — Guide for the Use of the International System of Units