Convert temperatures instantly. This free temperature converter switches between Celsius, Fahrenheit and Kelvin from any starting unit, with conversion formulas and a reference table of common temperatures.
Enter a temperature and pick its unit. The other two scales update instantly. Kelvin is an absolute scale, so it can’t go below 0 K (-273.15 °C).
Celsius and Fahrenheit meet at -40° (-40 °C = -40 °F). Water freezes at 0 °C / 32 °F / 273.15 K and boils at 100 °C / 212 °F / 373.15 K at sea level.
What This Temperature Converter Does
Enter a temperature in Celsius, Fahrenheit, or Kelvin, and this calculator converts it instantly to the other two scales, along with a plain-language reference for where that temperature sits (freezing, body temperature, boiling, and so on).
The Conversion Formulas
Fahrenheit = Celsius x 9/5 + 32
Celsius = (Fahrenheit - 32) x 5/9
Kelvin = Celsius + 273.15
For example, 25 °C converts to 77 °F and 298.15 K.
Where Celsius and Fahrenheit Meet
Celsius and Fahrenheit are equal at exactly -40 degrees (-40 °C = -40 °F) – the one point on both scales where the two numbers genuinely match, a useful quirk worth knowing when double-checking a conversion.
Why Kelvin Has No Negative Values
Kelvin is an absolute temperature scale starting at absolute zero, the theoretical point where all molecular motion stops. This is exactly -273.15 °C, meaning Kelvin can never go below 0 K – unlike Celsius and Fahrenheit, which both extend into negative numbers.
Reference Points Worth Knowing
Water freezes at 0 °C / 32 °F / 273.15 K and boils at 100 °C / 212 °F / 373.15 K at sea level. Normal human body temperature sits around 37 °C / 98.6 °F.
Why Kelvin Matters in Science
Kelvin is the standard temperature unit in scientific contexts because it has no negative values and is directly proportional to the actual thermal energy of a system – properties that make it more convenient than Celsius or Fahrenheit for physics and chemistry calculations.
Converting Recipe and Oven Temperatures
A recipe written for a 180 °C oven translates to about 356 °F, while a US recipe calling for 350 °F translates to about 177 °C. Since most home ovens only offer coarse dial increments, rounding to the nearest common setting (350 °F or 180 °C) is standard practice when following a recipe from a different unit system.
Converting Weather Forecasts
Checking the weather for an international trip often means translating an unfamiliar Celsius or Fahrenheit forecast into a scale you actually have an intuitive feel for. A forecast of 30 °C, for instance, converts to 86 °F – genuinely hot weather, which isn’t obvious from the number 30 alone to someone used to Fahrenheit.
How to Use the Temperature Converter
- Choose the starting unit: Celsius, Fahrenheit, or Kelvin.
- Enter your temperature, decimals included.
- Review the result across all three scales, plus a plain-language reference point.
Converting a length instead? See our Feet to Meters Converter.