Celsius to Fahrenheit Converter
Type a temperature in degrees Celsius and get the Fahrenheit value straight away, with kelvin as a bonus line. The page shows the formula with your numbers filled in, so you can check the answer or learn to do it by hand.
Last updated November 4, 2026
Any value from -273.15 (absolute zero) upward. Decimals are fine.
Result
25 °C = 77 °F
| Scale | Temperature |
|---|---|
| Fahrenheit | 77 °F |
| Kelvin | 298.15 K |
Show the work
Formula: °F = °C × 9/5 + 32
- Start with the Celsius value: 25 °C.
- Multiply by 9/5 (1.8): 25 × 9/5 = 45.
- Add 32: 45 + 32 = 77.
- Kelvin, for reference: 25 + 273.15 = 298.15 K.
Result: 25 °C = 77 °F
The Celsius to Fahrenheit formula
°F = °C × 9/5 + 32 (the same as °C × 1.8 + 32)
The two scales disagree about where to start and how big a degree is. On the Celsius scale, water freezes at 0 and boils at 100 under standard atmospheric pressure, so there are 100 degrees between the two points. On the Fahrenheit scale the same two points are 32 and 212, which is 180 degrees apart.
That ratio, 180 to 100, reduces to 9 to 5. So a Celsius degree is 1.8 times as large as a Fahrenheit degree, and the conversion first multiplies by 9/5 to rescale the size of the degree. It then adds 32 to move the zero point from the freezing point of water to the Fahrenheit zero.
The conversion is exact, not an approximation. Kelvin, shown as a secondary line, is simply the Celsius value plus 273.15, and 0 K, absolute zero, is -273.15 °C or -459.67 °F. Nothing can be colder, so this converter rejects anything below -273.15 °C and tells you why.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Also useful alongside this calculator: MPG Calculator and Pace Calculator.
A quick mental shortcut
For a rough answer without a calculator, double the Celsius value and add 30. For 20 °C that gives 70 °F, against an exact 68 °F. The shortcut drifts as temperatures rise, because 1.8 is not quite 2, so use it for weather, not for baking or lab work.
A slightly better version is to double the number, subtract a tenth of the result, and then add 32. For 20 °C: 40, minus 4, plus 32 is 68 °F, which is exact here.
Negative temperatures and the -40 point
The formula works unchanged for temperatures below zero: multiply by 9/5 and add 32. For -10 °C the multiplication gives -18, and adding 32 gives 14 °F.
The two scales show the same number at exactly -40. Check it: -40 × 9/5 is -72, and -72 + 32 is -40. It is the only point where °C and °F agree.
How this differs from the multi-unit converter
This page does one job: Celsius in, Fahrenheit out, with the working shown for that single direction. If you need to start from Fahrenheit or kelvin, or want all three scales at once, use the Temperature Converter, which is linked under related calculators below.
How to use the Celsius to Fahrenheit Converter
- Type the temperature in degrees Celsius into the box. Decimals and negative values are fine, down to -273.15.
- Read the Fahrenheit result in the headline, with the kelvin value below it.
- Open Show the work to see 9/5 multiplication and the addition of 32 with your own numbers.
- Compare against the table of common temperatures below if you want a sanity check.
- Use Copy, Print or Share to keep the result.
Worked example: 37 °C and other common points
Take normal body temperature, conventionally 37 °C. Multiply by 9/5: 37 × 9/5 = 66.6. Add 32: 66.6 + 32 = 98.6 °F. The same two steps give every other row of the table, including the oven setting of 180 °C, which is 180 × 9/5 + 32 = 356 °F.
| Point | °C | °F | K |
|---|---|---|---|
| Equal point of both scales | -40 | -40 | 233.15 |
| Water freezes | 0 | 32 | 273.15 |
| Cool room | 20 | 68 | 293.15 |
| Warm day | 25 | 77 | 298.15 |
| Normal body temperature | 37 | 98.6 | 310.15 |
| Water boils at sea level | 100 | 212 | 373.15 |
| Moderate oven | 180 | 356 | 453.15 |
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 (1.8) and add 32. For 25 °C that is 25 × 1.8 = 45, plus 32, which gives 77 °F.
What is 0 degrees Celsius in Fahrenheit?
It is 32 °F, the freezing point of water. The formula gives 0 × 9/5 = 0, and adding 32 leaves 32.
At what temperature are Celsius and Fahrenheit equal?
At -40. Because -40 × 9/5 + 32 equals -40, the two scales show the same number there and nowhere else.
Why does the converter refuse very low temperatures?
Nothing can be colder than absolute zero, which is -273.15 °C or -459.67 °F. Any lower Celsius value is physically impossible, so it is rejected with a message.
Is 37 °C always exactly normal body temperature?
No. 37 °C (98.6 °F) is the traditional average. Individual readings vary by person, time of day and measuring site, and this converter only does the arithmetic.