Celsius to FahrenheitFree online conversion calculator — instant results, no sign-up
Convert Celsius to Fahrenheit and back.
About the Celsius to Fahrenheit
The Celsius to Fahrenheit calculator converts a temperature in degrees Celsius to degrees Fahrenheit and also shows its Kelvin equivalent. With the default input of 25 °C, it returns 77 °F and 298.15 K. The reverse formula lets you convert a Fahrenheit temperature back to Celsius.
- Temperature (°C)
- The temperature to convert, entered in degrees Celsius (°C), with a default value of 25.
Formula and method
°F = °C × 9/5 + 32; K = °C + 273.15. Reverse conversion: °C = (°F − 32) × 5/9.
- °CThe numerical temperature value in degrees Celsius.
- °FThe numerical temperature value in degrees Fahrenheit.
- KThe numerical temperature value in kelvins, written without a degree symbol.
Multiply the Celsius input by 9/5, then add 32 to obtain Fahrenheit. Independently, add 273.15 to the Celsius input to obtain Kelvin. For the default input, 25 × 9/5 + 32 = 77 °F and 25 + 273.15 = 298.15 K. To convert back from Fahrenheit, subtract 32 before multiplying by 5/9.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Temperature25 °C
Results
- Fahrenheit77 °F
- Kelvin298.15 K
- Formula°F = °C × 9/5 + 32
How to use the Celsius to Fahrenheit
- 1Enter a value in Temperature (°C), or keep the default of 25.
- 2Read the Fahrenheit result: the default input produces 77 °F.
- 3Read the Kelvin result: the same input produces 298.15 K.
- 4Check the Formula row, °F = °C × 9/5 + 32, to see how the Fahrenheit result was calculated.
- 5For a reverse check, apply °C = (°F − 32) × 5/9 to the Fahrenheit result; 77 °F converts back to 25 °C.
Reading your result
The Fahrenheit row shows the entered Celsius temperature expressed in °F: 25 °C equals 77 °F. The Kelvin row expresses that same temperature on the absolute Kelvin scale: 298.15 K. The Formula row shows the Celsius-to-Fahrenheit rule, °F = °C × 9/5 + 32; these outputs describe the same temperature, not separate measurements.
Limitations
The conversion factors and offsets are exact, but displayed results may be rounded and cannot improve the accuracy of the original measurement. These formulas convert temperature readings, not temperature differences; differences do not use the additive offsets. For ordinary physical temperatures, inputs below absolute zero (−273.15 °C) are not valid, even if arithmetic produces a result. The listed input is Celsius only, so the reverse formula is provided without assuming a separate Fahrenheit input control.
Common questions
Why does 25 °C convert to 77 °F?+
The Fahrenheit scale has a different interval size and zero point: 25 × 9/5 + 32 = 77 °F.
How do I convert the Fahrenheit result back to Celsius?+
Subtract 32 from the Fahrenheit value, then multiply by 5/9. For the default result, (77 − 32) × 5/9 = 25 °C.
Why does this Celsius to Fahrenheit calculator also show 298.15 K?+
Kelvin is another way to express the same temperature. Adding 273.15 to the default Celsius input gives 25 + 273.15 = 298.15 K.
Can I use this formula to convert a Celsius temperature change?+
Not with the +32 offset. For a temperature change or difference, use Δ°F = Δ°C × 9/5; the offset applies only to temperature readings.
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.