How to convert °F to °C
°C = °F × 0.5555555556 − 17.77777778. The offset accounts for the different zero points of these temperature scales.
Worked example
A reading of 68 °F converts to 20 °C.
- Start with 68 °F.
- Apply °C = °F × 0.5555555556 − 17.77777778.
- Report 20 °C, rounded to the precision of your original measurement.
Subtract 32 before multiplying by 5/9. Multiplying first and then subtracting 32 gives the wrong result.
Check the reverse conversion
1 °C = 33.8 °F. Use the celsius to fahrenheit converter to calculate in the opposite direction. This has its own formula and reference table.
Definitions that matter
These formulas convert temperature readings. For a temperature change, use the scale factor without adding a zero-point offset. Readings below absolute zero are rejected.
The source scale maps to kelvin as K = °F × 0.5555555556 + 255.3722222. The destination conversion reverses its scale and zero-point offset.
Sources and precision
Definitions: BIPM SI Brochure. Calculations use double precision; the tool defaults to a readable rounded result, while tables show up to ten significant digits. Displaying more digits does not increase the accuracy of the original measurement.
Read our calculation methodology and content standards, or continue with temperature readings versus temperature differences.