// conversions › 1 · Basic Converters
Convert temperature between Celsius, Fahrenheit, Kelvin and Rankine using affine transforms via Kelvin.
K = f(value); target = g(K). Affine: °C+273.15; (°F−32)×5/9+273.15; °R×5/9
Because Celsius and Fahrenheit place their zero points at different physical temperatures than Kelvin. Converting needs an affine transform — a multiply AND an offset — so we route every value through Kelvin, the absolute scale, first.
100 °C to °F: 100 + 273.15 = 373.15 K, then (373.15 − 273.15) × 9/5 + 32 = 212 °F.
The radial gauge maps your temperature onto colour-banded comfort zones — freezing, comfortable, hot and danger — with a needle pointing to where your value sits, so the number has immediate physical meaning.
Weather, cooking, scientific work (Kelvin), and engineering thermodynamics, where Rankine still appears in some US aerospace and HVAC calculations.
Nothing can be colder than absolute zero (0 K = −273.15 °C). If a conversion would produce a sub-zero-Kelvin result, the calculator flags it rather than returning a physically impossible value.