Temperature Converter

Temperature looks like the simplest thing to convert until you try, because Celsius, Fahrenheit, and Kelvin don’t share a zero. Celsius and Fahrenheit are offset scales whose zero points were set by convention, while Kelvin starts at absolute zero, the coldest anything can physically get.

Celsius to Fahrenheit: °F = (°C × 9/5) + 32

Fahrenheit to Celsius: °C = (°F - 32) × 5/9

Celsius to Kelvin: K = °C + 273.15

Kelvin to Celsius: °C = K - 273.15

Reference points:

• Water freezes: 0°C = 32°F = 273.15 K
• Water boils: 100°C = 212°F = 373.15 K
• Body temperature: 37°C = 98.6°F = 310.15 K
• Absolute zero: -273.15°C = -459.67°F = 0 K

The “+32” is what catches people. You can’t convert a temperature difference the same way you convert a temperature. A rise of 10°C is a rise of 18°F, not 50°F, because the offset applies to the reading, not to the gap between two readings.

It’s also why “twice as hot” is meaningless in Celsius or Fahrenheit. 20°C is not twice as hot as 10°C in any physical sense. Only on the Kelvin scale, which begins at true zero, does doubling the number actually double the thermal energy. For everyday weather, Celsius and Fahrenheit are fine; for physics, you almost always want Kelvin.