Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin temperature scales
Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin
Quick Reference
Conversion Formulas
Guide
How it works
This temperature converter moves a reading between the three scales people actually use: Celsius, Fahrenheit, and Kelvin. Type a value in any one and read the equivalent in the others. It is the tool for a recipe written in Fahrenheit when your oven shows Celsius, a weather forecast in the unfamiliar scale, or a science problem that demands Kelvin. Unlike length or weight, temperature scales do not simply scale by a single factor, which is exactly why a dedicated converter is so useful.
Why temperature is different
Most conversions multiply by a fixed number, but temperature scales have different zero points as well as different step sizes, so converting needs both a multiplication and an addition. Celsius sets zero at the freezing point of water and 100 at its boiling point. Fahrenheit puts those same two points at 32 and 212, spreading 180 degrees across the range where Celsius uses 100. Kelvin keeps the Celsius step size but starts at absolute zero, the coldest temperature physically possible, which sits at -273.15 degrees Celsius.
The formulas
- Celsius to Fahrenheit: F = (C times 9/5) + 32
- Fahrenheit to Celsius: C = (F - 32) times 5/9
- Celsius to Kelvin: K = C + 273.15
- Kelvin to Celsius: C = K - 273.15
A worked example
Take a warm day of 30 degrees Celsius. Multiply by 9/5 to get 54, then add 32, which gives 86 degrees Fahrenheit. To express the same temperature in Kelvin, add 273.15 to the Celsius figure, giving 303.15 Kelvin. Notice that the addition step is what trips people up in mental math: forgetting to add 32 turns a pleasant 86 Fahrenheit into a meaningless 54, which is why letting the converter handle both steps avoids easy errors.
Reference points worth knowing
- Water freezes at 0 degrees Celsius, 32 degrees Fahrenheit, 273.15 Kelvin.
- A comfortable room is about 20 to 22 degrees Celsius, or 68 to 72 degrees Fahrenheit.
- Normal human body temperature is about 37 degrees Celsius, or 98.6 degrees Fahrenheit.
- Water boils at 100 degrees Celsius, 212 degrees Fahrenheit, 373.15 Kelvin (at sea level).
- The scales cross at -40, where -40 degrees Celsius equals -40 degrees Fahrenheit.
Kelvin is written without the word "degrees" - a reading is "300 kelvin," not "300 degrees kelvin" - and is standard in science because it has no negative values, making it the natural scale for physics and chemistry.
How do I convert Celsius to Fahrenheit?expand_more
Multiply the Celsius value by 9/5 (which is 1.8), then add 32. For example, 25 degrees Celsius is (25 times 1.8) + 32 = 77 degrees Fahrenheit.
How do I convert Fahrenheit to Celsius?expand_more
Subtract 32 from the Fahrenheit value, then multiply by 5/9. For example, 98.6 degrees Fahrenheit is (98.6 - 32) times 5/9 = 37 degrees Celsius, normal body temperature.
What is Kelvin and when is it used?expand_more
Kelvin is the scientific temperature scale that starts at absolute zero, the lowest possible temperature. It uses the same step size as Celsius, so you convert by adding 273.15 to a Celsius value. It is standard in physics and chemistry because it has no negative numbers.
At what temperature do Celsius and Fahrenheit read the same?expand_more
At -40 degrees. Minus 40 Celsius and minus 40 Fahrenheit are exactly the same temperature, the single point where the two scales cross.
Why can't I just multiply to convert temperatures?expand_more
Because the scales have different zero points as well as different step sizes. A simple multiplication only works when both scales start at the same zero. Temperature needs both a multiply and an add (or subtract), which is why the formulas include the +32 or +273.15 step.
What oven temperature in Celsius equals 350 Fahrenheit?expand_more
About 177 degrees Celsius, which most ovens and recipes round to 175 or 180. To convert, subtract 32 from 350 to get 318, then multiply by 5/9. This is one of the most common kitchen conversions, since many recipes are written in Fahrenheit.
Is there a lowest possible temperature?expand_more
Yes. Absolute zero, 0 Kelvin or about -273.15 degrees Celsius, is the coldest temperature physically possible, the point at which particle motion is at its minimum. Nothing can be colder, which is why the Kelvin scale starts there and never goes negative.