°C = (°F − 32) × 5 ÷ 9
Temperature scales require both a scale and an offset.Conversion lab / temperature
Fahrenheit to Celsius Converter
Convert degrees Fahrenheit to degrees Celsius with the standard offset-and-scale formula.
Fahrenheit to Celsius Converter: Read a Fahrenheit oven setting, weather report or instrument display in Celsius. The calculation first removes Fahrenheit's offset, then changes the size of the degree. Use the source reading rather than an already rounded estimate when you need to compare two displays. Runs 100% locally in your browser with zero server file uploads.
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Result / live
-17.22222222
°Cdegrees Celsius
-40 °F-40 °C
0 °F-17.77777778 °C
32 °F0 °C
68 °F20 °C
212 °F100 °C
Degrees Fahrenheit to degrees Celsius conversion table
| degrees Fahrenheit (°F) | degrees Celsius (°C) |
|---|---|
| -40 °F | -40 °C |
| -20 °F | -28.88889 °C |
| 0 °F | -17.77778 °C |
| 20 °F | -6.666667 °C |
| 32 °F | 0 °C |
| 40 °F | 4.444444 °C |
| 60 °F | 15.55556 °C |
| 68 °F | 20 °C |
| degrees Fahrenheit (°F) | degrees Celsius (°C) |
|---|---|
| 80 °F | 26.66667 °C |
| 100 °F | 37.77778 °C |
| 120 °F | 48.88889 °C |
| 140 °F | 60 °C |
| 160 °F | 71.11111 °C |
| 180 °F | 82.22222 °C |
| 200 °F | 93.33333 °C |
| 212 °F | 100 °C |
Rounded to seven significant digits; the converter above uses the full factor.
Converting an oven reading
With F as degrees Fahrenheit and C as degrees Celsius, C = (F − 32) × 5/9. At 350 °F, subtract 32 to get 318, multiply by 5 to get 1,590 and divide by 9 to get 176.666666… °C. The converter displays 176.66666667 °C to eight decimal places. Round only at the end if copying the answer onto a dial.
NIST's conversion table (https://www.nist.gov/pml/owm/si-units-temperature) distinguishes exact conversions from approximate oven equivalents. The equation is affine: the non-zero offset prevents a proportional relationship between the readings.
The crossover and absolute scale
At −40 °F the subtraction gives −72; multiplying by 5/9 yields −40 °C. That equality follows from solving x = (x − 32) × 5/9, rather than from equal degree sizes. Celsius retains a degree sign. If you later express the result in kelvin, use the symbol K without °, and add 273.15 to the Celsius reading.
How to use it
- Enter the temperature in degrees Fahrenheit.
- Read the converted degrees Celsius value as it updates.
- Use the common values or open the reverse conversion to cross-check.
Privacy & limitations
Your value never leaves this browser. JavaScript floating-point arithmetic can round the last displayed digit; this general utility is not a substitute for calibrated or regulated measurement systems.
Related tools
Frequently asked questions
Should I subtract 32 before or after dividing?
Subtract 32 first, then multiply by 5/9. For example, 68 − 32 = 36 and 36 × 5/9 = 20 °C. Dividing 68 by 1.8 and then subtracting 32 puts the offset in the wrong place.
Why is a 350 °F oven setting not exactly 180 °C?
Its exact conversion is 176.666666… °C. A recipe or oven dial may round to a convenient setting such as 180 °C. That practical rounding does not change the scale relationship, and fan-oven adjustments are a separate cooking convention.
How do I convert a Fahrenheit temperature drop?
For a drop of 18 °F, multiply only by 5/9 to get a 10 °C drop. Subtracting 32 would treat the size of the change as a temperature reading. Preserve the direction: a signed change of −18 °F becomes −10 °C.
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