Fahrenheit to Celsius formula
Temperature scales start at different points, so the conversion has an offset as well as a ratio. To convert degrees Fahrenheit to degrees Celsius use: °C = (°F − 32) × 5/9.
One degree Fahrenheit equals -17.2222222222 degrees Celsius, and one degree Celsius equals 33.8 degrees Fahrenheit. The rule C = (F - 32) x 5/9 is exact. It is not a simple ratio because the scales start at different points, so you must subtract 32 first.
Worked example
Suppose you have 98.6 degrees Fahrenheit and need the answer in degrees Celsius.
- Write the formula: °C = (°F − 32) × 5/9.
- Put in 98.6 °F and work it out: 37 °C.
- Round to suit the job. 37 °C is accurate enough for most everyday uses.
So 98.6 °F is 37 °C. To check, convert back: 37 °C is 98.6 °F.
Common degrees Fahrenheit to degrees Celsius values
| degrees Fahrenheit (°F) | degrees Celsius (°C) |
|---|---|
| 1 | -17.22222222 |
| 2 | -16.66666667 |
| 5 | -15 |
| 10 | -12.22222222 |
| 20 | -6.666666667 |
| 50 | 10 |
| 100 | 37.77777778 |
Reference points
Some familiar amounts in degrees Fahrenheit, converted to degrees Celsius:
- 32 °F, water freezes: 0 °C
- 72 °F, a pleasant room: 22.2222 °C
- 98.6 °F, normal body temperature: 37 °C
- 350 °F, a common baking temperature: 176.667 °C
Where you will use it
American weather reports, thermometers, ovens and fever checks are in Fahrenheit, while the rest of the world works in Celsius. Travelers and cooks use this direction to make sense of US sources.
Quick mental math
Subtract 30 and halve. 72 F becomes 21 by this shortcut, and the exact answer is 22.2 C. Rule of thumb: multiply by 0.5, then subtract 15. For 98.6 °F this gives 34.3 °C against the exact 37, an error of 7.3 percent.
Going the other way
Need the reverse? Use the Celsius to Fahrenheit converter. For comparison, 98.6 °C is 209.48 °F. To compare every temperature unit at once, open the temperature converter.
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