Fahrenheit, Celsius and Kelvin formulas
Temperature scales have different zero points, so you cannot convert them with a single factor: it is a factor plus an offset. The Kelvin is the SI unit (absolute zero = 0 K); Rankine is the absolute scale with Fahrenheit-sized degrees, still used in US engineering thermodynamics.
°C = (°F − 32) × 5/9 °F = °C × 9/5 + 32
K = °C + 273.15 °R = °F + 459.67
−40 °F = −40 °C (the two scales cross)
Fahrenheit to Celsius chart (cooking and weather)
| °F | °C | K |
|---|---|---|
| -40 °F | -40 | 233.1 |
| 0 °F | -17.8 | 255.4 |
| 32 °F | 0 | 273.1 |
| 50 °F | 10 | 283.1 |
| 68 °F | 20 | 293.1 |
| 98.6 °F | 37 | 310.1 |
| 100 °F | 37.8 | 310.9 |
| 212 °F | 100 | 373.1 |
| 250 °F | 121.1 | 394.3 |
| 300 °F | 148.9 | 422 |
| 325 °F | 162.8 | 435.9 |
| 350 °F | 176.7 | 449.8 |
| 375 °F | 190.6 | 463.7 |
| 400 °F | 204.4 | 477.6 |
| 425 °F | 218.3 | 491.5 |
| 450 °F | 232.2 | 505.4 |
Worked example
A recipe calls for 350 °F: (350 − 32) × 5/9 = 176.67 °C, which ovens round to 180 °C (fan ovens about 160 °C). A temperature difference converts without the offset: a 10 °F rise is 10 × 5/9 = 5.56 °C.
Frequently asked questions
How do I convert Fahrenheit to Celsius?
Subtract 32 and multiply by 5/9. Example: 100 °F − 32 = 68; 68 × 5/9 = 37.78 °C.
What is 180 °C in Fahrenheit?
356 °F. Ovens usually call it 350 °F.
At what temperature are °F and °C equal?
At −40: −40 °F = −40 °C.