Temperature Converter: Celsius, Fahrenheit, and Kelvin
Temperature scales have different zero points, so conversion uses both a scale factor and an offset. This tool converts a value between Celsius, Fahrenheit, and Kelvin.
How to use this tool
- Enter the temperature value.
- Choose its current scale.
- Choose the scale you want.
- Click Convert to display the converted value.
- Use Swap units to reverse the direction.
Options explained
The converter supports Celsius (°C), Fahrenheit (°F), and Kelvin (K). Unlike length or mass conversion, temperature conversion cannot be done by multiplying by one constant because the scale origins differ.
Accuracy and limitations
Displayed values are rounded. For laboratory, industrial, or safety-critical work, confirm required precision and calibration against the relevant equipment or standard.
The formulas
To change Celsius into Fahrenheit multiply by 9/5 and add 32. To change Fahrenheit into Celsius subtract 32 and multiply by 5/9. Kelvin is Celsius plus 273.15, so subtract 273.15 from a Kelvin value to get Celsius. Because the scales start at different points, you cannot convert by multiplying with one constant, which is why a converter is useful.
Handy reference points
Water freezes at 0 C, which is 32 F and 273.15 K, and boils at 100 C, which is 212 F and 373.15 K at sea level. A comfortable room is about 20 to 22 C, or 68 to 72 F. The two scales meet at -40, where Celsius and Fahrenheit show the same number. Absolute zero is 0 K, which is -273.15 C, and nothing can be colder.
Cooking and everyday use
Ovens are often marked in one scale while a recipe uses the other. 180 C is 356 F, 200 C is 392 F and 220 C is 428 F. Weather forecasts, heaters, air conditioners and imported appliances can also use a different scale from the one you know. Enter the value, pick the scale it is in and the scale you want, and use Swap units to go back.
Rounding and precision
The displayed value is rounded. For cooking and weather this is more than enough, but for laboratory work, industrial settings or safety-critical equipment you should use the precision the standard requires and check your thermometer or sensor, because the converter does not know how accurate your instrument is.
Frequently asked questions
What is the formula to convert Celsius to Fahrenheit?
Fahrenheit = Celsius x 9/5 + 32. For example 25 C is 77 F. To convert back, Celsius = (Fahrenheit - 32) x 5/9.
At what temperature are Celsius and Fahrenheit equal?
At -40. Minus 40 C and minus 40 F are the same temperature.
Why can I not convert with one multiplier?
The zero points of the scales are different, so you must multiply and also add or subtract an offset.
Can a temperature in Kelvin be negative?
No. Kelvin starts at absolute zero, 0 K, which is -273.15 C.
How do I convert an oven setting from Celsius to Fahrenheit?
Multiply by 9/5 and add 32. For example 200 C is 392 F.
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