Temperature Converter (°C, °F, K)

Celsius to Fahrenheit: °F = °C × 9/5 + 32. Fahrenheit to Celsius: °C = (°F − 32) × 5/9. Kelvin is Celsius plus 273.15. So 100 °C = 212 °F = 373.15 K (water boils), and 0 °C = 32 °F = 273.15 K (water freezes).

Celsius puts 0 and 100 at the freezing and boiling points of water. Fahrenheit uses older reference points, which land those same events at 32 and 212 — a 180-degree span against Celsius's 100, hence the 9/5 ratio and the +32 offset. Kelvin starts at absolute zero (−273.15 °C), the point where thermal motion stops, and is the SI base unit for temperature.

Double the Celsius and add 30: 20 °C → about 70 °F (true value 68 °F). It drifts at the extremes but is fine for weather. Worth memorizing: −40 is the same number on both scales, 37 °C ≈ 98.6 °F is body temperature, and 180 °C ≈ 350 °F is a common oven setting.