Degrees Fahrenheit to degrees Celsius converter

Read a quantity in °F, then express the same temperature in °C. The units are defined below to avoid mixing similarly named standards.

Direct example

20 °F ≈ -6.66666666667 °C.

Formula and calculation

°C = (°F × 0.555555555556 + -17.7777777778 − (0)) ÷ 1

Substituting 20 °F gives approximately -6.66666666667 °C. Definitions use the constants above; arithmetic uses browser floating point and displays at most 12 significant digits. The rounded table is not an instrument calibration or certified measurement.

Which units does this page use?

degrees Fahrenheit: Fahrenheit temperature scale; 32 °F equals 0 °C.

degrees Celsius: Celsius temperature scale; 0 °C equals 273.15 K.

When this direction is useful

Start here when your source record uses °F for US temperature displays and recipe temperatures, but the receiving specification is expressed in °C for weather reports and appliance settings. Enter the original quantity rather than reusing a previously rounded result. If your source uses °C, use the reverse converter instead.

Conversion table

Approximate displayed values, with the same definitions as the converter
degrees Fahrenheit (°F)	degrees Celsius (°C)
-40	-40
0	-17.7777777778
20	-6.66666666667
37	2.77777777778
100	37.7777777778

Limits and interpretation

This converts a temperature reading, not a temperature difference. The scale offsets matter. Values below absolute zero are rejected. Use a decimal dot; grouping commas are not accepted. No external rates, live data or account are involved.

Frequently asked questions

Can I convert the other way?

Yes. Convert degrees Celsius to degrees Fahrenheit with the inverse equation. Rounding a result before converting it back can introduce a small difference.

Are these the same as every similarly named unit?

No. Check the two definitions above. International length, avoirdupois mass, US customary liquid measures and temperature readings are explicitly distinguished; an ambiguous label on a source document must be resolved first.

Where do the conversion definitions come from?

They use SI and defined customary conversion relationships. See the NIST Guide for the Use of SI. Output formatting is this tool's display policy, not extra measurement accuracy.