Fahrenheit to Celsius converter, °F to °C, exactly.

To convert Fahrenheit to Celsius, subtract 32 and then divide by 1.8. So 70 °F is (70 − 32) ÷ 1.8 = 21.11 °C, 212 °F is 100 °C and 32 °F is 0 °C. The same rule works for negative numbers: -4 °F is -20 °C. Unlike lengths and weights, temperature has an offset, so a single multiplication does not work.

How to use the converter

1. Type a temperature in the Degrees Fahrenheit (°F) box. A minus sign works, for example -4.
2. The big result shows Degrees Celsius (°C), rounded to two places. Change Decimals for more or fewer.
3. Type Celsius in the other box to get Fahrenheit. The card shows the kelvin value too.
4. Click a row in Common values for oven, weather and freezing points, or use the Up and Down arrow keys to step by 1 degree.
5. Press Print chart for an oven chart to stick on the fridge.

The exact formula

NIST Handbook 44 (2026), Appendix C has a table "Conversion Equations for Units of Temperature (Exact)". It gives degree Celsius = (degree Fahrenheit − 32) ÷ 1.8 and kelvin = that value + 273.15. NIST Special Publication 811, Appendix B.8 gives the same: t/°C = (t/°F − 32)/1.8, with 32 and 1.8 in boldface as exact. Both were checked 18 Oct 2026. Both constants are exact, and so is the answer: 98.6 °F is 37 °C with no rounding hidden in the formula.

A shortcut for weather, and its error

Subtract 30 and halve. 70 °F: 70 − 30 = 40, half is 20 °C. The exact answer is 21.11, so it is 1.11 °C low. The shortcut is best near 50 °F, where it is exact, and drifts as you move away. At 32 °F it says 1 °C against 0. At 86 °F it says 28 °C against 30. Between 14 °F and 86 °F it stays within about 2 °C of the true value. For cooking and for science, use the formula.

The reverse trick, Celsius to Fahrenheit, is to double and add 30. 20 °C gives 70 °F by the trick. The exact answer is 20 × 1.8 + 32 = 68 °F, so the trick is 2 °F high here.

Worked examples

• An oven at 350 °F. 350 − 32 = 318. 318 ÷ 1.8 = 176.67 °C. An oven at 425 °F is 218.33 °C, and one at 400 °F is 204.44 °C.
• A room at 72 °F. 72 − 32 = 40. 40 ÷ 1.8 = 22.22 °C.
• A freezing night, 0 °F. 0 − 32 = -32. -32 ÷ 1.8 = -17.78 °C.
• A thermometer reading 98.6 °F. 98.6 − 32 = 66.6. 66.6 ÷ 1.8 = 37 °C. This is a conversion, not a medical reading.
• A forecast of 95 °F. 95 − 32 = 63. 63 ÷ 1.8 = 35 °C.

Mistakes that are specific to temperature

The two scales meet at -40: -40 °F is -40 °C, which is a handy check for your sums. The most common error is halving first and subtracting later, or forgetting the brackets: 70 − 32 ÷ 1.8 is 52.2, not 21.1. A second is mixing up a reading with a change. A reading of 70 °F is 21.1 °C, but a rise of 10 °F is only a rise of 10 × 5/9 = 5.56 °C, with no 32 involved. A third is dropping the minus sign on a cold day: -4 °F is -20 °C, not 20.

Oven settings and weather

The table shows common oven temperatures and weather readings in Fahrenheit with the exact Celsius value to one decimal.

A 350 °F recipe is 176.7 °C, so set a Celsius dial to the nearest mark and follow the recipe if it says to lower the setting for a fan oven. That is a cooking matter and not a conversion matter.

Cold and hot extremes

Negative numbers behave the same way. -40 °F and -40 °C are equal. -10 °F is -23.3 °C and -22 °F is -30 °C. At the other end, 100 °F is 37.8 °C and 120 °F is 48.9 °C. For a scientist, the kelvin card shows the absolute value: 0 °C is 273.15 K and so 32 °F is also 273.15 K. A kelvin has no degree sign and is never negative.

Who uses Fahrenheit to Celsius

Cooks with an oven in one scale and a recipe in the other. Travellers reading a forecast. Anyone with a thermometer, a fridge or a freezer set for a different country. Students in a science lesson. For lengths see the CM to inches converter, for weights the KG to LBS converter, and for kitchen volume the Ounces to cups converter.