Celsius to Fahrenheit: Conversion Formulas and Quick Tricks
The exact formulas to convert between Celsius, Fahrenheit, and Kelvin, a fast mental-math shortcut, and handy reference points you can memorize.
Temperature conversion is one of the most searched calculations in the world, because different countries use different scales. Whether you are reading a recipe, checking the weather abroad, or working through a science problem, knowing how to convert quickly is genuinely useful.
The Conversion Formulas
Celsius to Fahrenheit: F = (C x 9/5) + 32
Fahrenheit to Celsius: C = (F - 32) x 5/9
Celsius to Kelvin: K = C + 273.15
Example: 25 C to Fahrenheit
(25 x 9/5) + 32 = 77 FA Quick Mental Math Trick
For a fast approximation from Celsius to Fahrenheit, double the Celsius value and add 30. For 20 C, that gives about 70 F (the exact answer is 68 F). It is not perfect, but it is close enough for everyday weather estimates when you do not have a calculator handy.
Useful Reference Points
- Water freezes: 0 C = 32 F
- Room temperature: about 21 C = 70 F
- Normal body temperature: 37 C = 98.6 F
- Water boils: 100 C = 212 F
Memorizing a few reference points, like 0 C = 32 F and 37 C = 98.6 F, lets you sanity-check any conversion instantly.
For precise results across Celsius, Fahrenheit, and Kelvin, the Temperature Converter gives you an exact answer as you type.