Fahrenheit to CelsiusFree online conversion calculator — instant results, no sign-up
Convert Fahrenheit to Celsius and back.
About the Fahrenheit to Celsius
The Fahrenheit to Celsius calculator converts a temperature entered in degrees Fahrenheit into degrees Celsius and also shows its Kelvin equivalent. With the default input of 77 °F, it returns 25 °C and 298.15 K. The reverse formula below explains how to convert Celsius back to Fahrenheit.
- Temperature (°F)
- The temperature to convert, measured in degrees Fahrenheit, with a default value of 77.
Formula and method
°C = (°F − 32) × 5/9; Kelvin: K = °C + 273.15; reverse conversion: °F = °C × 9/5 + 32.
- °FThe numerical temperature value in degrees Fahrenheit.
- °CThe numerical temperature value in degrees Celsius.
- KThe numerical temperature value in kelvins, written without a degree symbol.
Subtract 32 from the Fahrenheit input, then multiply the result by 5/9 to obtain Celsius. Add 273.15 to the Celsius result to obtain Kelvin. For the default input, (77 − 32) × 5/9 = 25 °C, and 25 + 273.15 = 298.15 K. To convert back, multiply the Celsius value by 9/5 and add 32.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Temperature77 °F
Results
- Celsius25 °C
- Kelvin298.15 K
- Formula°C = (°F − 32) × 5/9
How to use the Fahrenheit to Celsius
- 1Enter the Fahrenheit temperature in Temperature (°F), or leave the default value of 77.
- 2Read the Celsius result calculated using °C = (°F − 32) × 5/9.
- 3Read the Kelvin result, calculated by adding 273.15 to the Celsius value.
- 4Check the Formula row to confirm the Fahrenheit-to-Celsius equation used.
- 5To convert the Celsius result back to Fahrenheit, use °F = °C × 9/5 + 32; the default result of 25 °C converts back to 77 °F.
Reading your result
The Celsius row shows the converted temperature in degrees Celsius: 25 °C for the default input of 77 °F. The Kelvin row shows the same temperature on the Kelvin scale: 298.15 K. The Formula row displays °C = (°F − 32) × 5/9, the equation used for the primary conversion. These outputs describe the same temperature, not different measurements.
Limitations
The conversion constants are exact, but displayed results may be rounded, and conversion does not improve the accuracy of the original measurement. These equations convert temperature readings, not temperature differences; differences use only the scale factor, without the offset. Ordinary physical temperatures cannot be below absolute zero, which is −459.67 °F, −273.15 °C, or 0 K; a mathematically computed value below that limit is not an ordinary physical temperature. The specified input is Fahrenheit, so the reverse equation is provided without assuming a separate Celsius input control.
Common questions
Why does 77 °F equal 25 °C?+
The Fahrenheit and Celsius scales have different zero points and degree sizes. Subtracting 32 from 77 and multiplying by 5/9 gives exactly 25 °C.
Why does the calculator show 298.15 K alongside 25 °C?+
Kelvin and Celsius use equal-sized increments, but their zero points differ by 273.15. Adding 273.15 to 25 °C gives 298.15 K.
How do I convert the Celsius result back to Fahrenheit?+
Use °F = °C × 9/5 + 32. For the default result, 25 × 9/5 + 32 gives 77 °F.
Can I use this Fahrenheit input to convert a temperature change?+
Not directly: this calculator applies the 32-degree offset needed for temperature readings. To convert a temperature change from Fahrenheit to Celsius, multiply the change by 5/9 without subtracting 32.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.