How to Convert Celsius to Fahrenheit (and Back)
Two scales, two different zero points. That is why temperature conversion needs two steps, not just a multiplication.
Celsius to Fahrenheit
°F = °C × 9 ÷ 5 + 32
For 25°C: 25 × 1.8 = 45, then 45 + 32 = 77°F.
Fahrenheit to Celsius
°C = (°F − 32) × 5 ÷ 9
For 98.6°F: 98.6 − 32 = 66.6, then × 5 ÷ 9 = 37°C.
Mental shortcut
Double the Celsius value and add 30. For 20°C that gives 70°F, close to the exact 68°F. It drifts at higher temperatures, so use it only for a quick feel.
Reference points
| Situation | °C | °F |
|---|---|---|
| Water freezes | 0 | 32 |
| Comfortable room | 22 | 71.6 |
| Normal body temperature | 37 | 98.6 |
| Water boils | 100 | 212 |
One more fact
The two scales meet at −40, where both read the same number.
Everyday uses
Weather apps, ovens and thermometers often use different scales when you travel or follow a foreign recipe. An oven set to 180°C is 356°F, usually shown as 350°F on American dials. For a fever check, 38°C is 100.4°F. Knowing the formula means you do not have to guess when a label shows only one scale.
Kelvin is a third scale used in science. To get it from Celsius, simply add 273.15, so 25°C is 298.15 K. Kelvin never goes below zero, which is why scientists prefer it. For daily life, though, Celsius and Fahrenheit are enough, and the two formulas above cover every case you are likely to meet at home, in the kitchen or while travelling.
Try it yourself
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