Celsius to Fahrenheit
°F = °C × 9/5 + 32 = °C × 1.8 + 32
The 1.8 factor comes from 180 °F ÷ 100 °C between freezing and boiling water.
Convert °C to °F (and °F to °C)
Celsius ↔ Fahrenheit converter in both directions: exact formula, mental-math shortcut, the −40 crossover, body temperature (37 °C = 98.6 °F), oven temperatures and real examples, including the trap of converting a temperature difference.
Conversion table
| °C | °F |
|---|---|
| -40 °C | -40 °F |
| -20 °C | -4 °F |
| -10 °C | 14 °F |
| 0 °C | 32 °F |
| 10 °C | 50 °F |
| 20 °C | 68 °F |
| 25 °C | 77 °F |
| 30 °C | 86 °F |
| 37 °C | 98.6 °F |
| 40 °C | 104 °F |
| 100 °C | 212 °F |
| °F | °C |
|---|---|
| -40 °F | -40 °C |
| 0 °F | -17.7778 °C |
| 32 °F | 0 °C |
| 50 °F | 10 °C |
| 68 °F | 20 °C |
| 77 °F | 25 °C |
| 86 °F | 30 °C |
| 98.6 °F | 37 °C |
| 104 °F | 40 °C |
| 212 °F | 100 °C |
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How does this tool work?
This converter turns degrees Celsius (°C) into degrees Fahrenheit (°F) and back: type a temperature in either field and the other updates instantly. Use it to read a weather forecast or recipe written in the other scale, set an oven whose dial is in °F, make sense of a body temperature reading or follow a technical sheet that uses the other scale.
Both scales are anchored on water at normal atmospheric pressure: 0 °C and 32 °F at freezing, 100 °C and 212 °F at boiling. That is 100 Celsius degrees but 180 Fahrenheit degrees between the two marks, so one Celsius degree equals 1.8 °F (9/5). Since 2019 the Celsius scale is defined through the kelvin (t in °C = T in K − 273.15), which is itself fixed by the Boltzmann constant.
To go from Celsius to Fahrenheit, multiply by 1.8 and add 32: °F = °C × 1.8 + 32. To go back, subtract 32 and divide by 1.8: °C = (°F − 32) ÷ 1.8. The two scales cross at −40: −40 °C = −40 °F, and absolute zero (−273.15 °C) is −459.67 °F.
For a quick mental estimate, double the Celsius value, take off 10% of the result, then add 32: 25 °C → 50 − 5 + 32 = 77 °F (exact). In the other direction, subtract 32, halve it, then add 10%: 68 °F → 36 ÷ 2 = 18, plus 10% ≈ 20 °C. Handy anchors: 0 °C = 32 °F, 10 °C = 50 °F, 20 °C = 68 °F, 30 °C = 86 °F.
Do not mix up a temperature with a temperature difference. A temperature uses the full formula, but a difference uses the 1.8 factor alone: a rise of 10 °C is a rise of 18 °F, not 50 °F. And do not confuse Fahrenheit with the kelvin, which has no degree symbol and whose interval is the same as the Celsius degree.
How to use this tool
Type a temperature
In the Celsius field or the Fahrenheit field; negative values and decimals are accepted.
Read the conversion
The other field recalculates on every keystroke with the exact formula, with no intermediate rounding.
Check the table
The table under the converter lists common reference points: 0, 20, 37 and 100 °C, but also 32, 68, 98.6 and 212 °F.
°C ↔ °F conversion formulas
The two scales are related by an affine function: a scale factor of 9/5 and an offset of 32 degrees.
Fahrenheit to Celsius
°C = (°F − 32) × 5/9
First remove the 32-degree offset, then change scale.
Temperature difference
Δ°F = Δ°C × 1.8
A difference carries no offset: never add 32.
- °C
- temperature in degrees Celsius (0 °C = 273.15 K)
- °F
- temperature in degrees Fahrenheit (32 °F = 0 °C)
- Δ
- difference between two temperatures, converted without the 32 offset
Example: 25 °C = 25 × 1.8 + 32 = 77 °F; a change of 25 °C, however, is 25 × 1.8 = 45 °F.
Use cases
Cooking and baking
Set an oven or a cooking thermometer from a recipe written in °F or °C.
Travel
Understand a weather forecast, a hotel thermostat or a pool temperature shown in the other scale.
Health and home
Convert a medical thermometer or a room thermostat reading from a foreign device.
Science and engineering
Read a datasheet or paper whose temperatures are written in the other scale.
Examples
Body temperature
37 × 1.8 + 32 = 98.6 °F; a 38 °C fever is 100.4 °F.
Input
37 °CResult
98.6 °FBaking oven
180 × 1.8 + 32 = 356 °F, which US recipes round to 350 °F.
Input
180 °CResult
356 °FAmerican recipe
(425 − 32) ÷ 1.8 = 218.33 °C, a hot oven you would set near 220 °C.
Input
425 °FResult
218.33 °CSummer day
35 × 1.8 + 32 = 95 °F, a heat wave as seen from New York or Miami.
Input
35 °CResult
95 °FWhere the scales meet
−40 × 1.8 + 32 = −40: the only temperature where both scales show the same number.
Input
−40 °CResult
−40 °FTips and best practices
- Anchor points: 0 °C = 32 °F, 20 °C = 68 °F, 37 °C = 98.6 °F, 100 °C = 212 °F.
- Every 10 °C adds 18 °F: 10 °C = 50 °F, 20 °C = 68 °F, 30 °C = 86 °F.
- A temperature difference uses the factor 1.8 alone, with no +32.
- In an oven, a 5 to 10 °C gap rarely matters: rounding 356 °F to 350 °F is fine.
- For an absolute temperature in kelvins, add 273.15 to the Celsius value.
Sources and references
- NIST, SI Units – Temperature (opens in a new tab)Page in English
- BIPM, The International System of Units (SI Brochure) (opens in a new tab), Bureau international des poids et mesuresPage in English
Frequently asked questions
How do you convert Celsius to Fahrenheit?
Multiply by 1.8 and add 32: °F = °C × 1.8 + 32. For example, 20 °C is 20 × 1.8 + 32 = 68 °F.
How do you convert Fahrenheit to Celsius?
Subtract 32 and divide by 1.8: °C = (°F − 32) ÷ 1.8. For example, 350 °F is (350 − 32) ÷ 1.8 ≈ 176.7 °C.
What is 37 °C in Fahrenheit?
37 °C is exactly 98.6 °F, the usual average body temperature. A 38 °C fever is 100.4 °F and 40 °C is 104 °F.
Why is −40 °C equal to −40 °F?
Because the scales have different zero points and different degree sizes: the equation x = 1.8x + 32 has a single solution, x = −40.
What is 180 °C in Fahrenheit for an oven?
180 °C is 356 °F; US recipes say 350 °F. 200 °C is 392 °F (400 °F) and 220 °C is 428 °F (425 °F).
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