Temperature Converter

Convert between Celsius, Fahrenheit, Kelvin, Rankine and Réaumur — accurate to industrial calibration standards.

Temperature scales are not proportional to each other, so conversions use exact affine formulas rather than a single multiplying factor: K = °C + 273.15; °R = °F + 459.67; °F = °C × 9/5 + 32; °Re = °C × 4/5. Values below absolute zero (0 K / −273.15 °C / −459.67 °F / 0 °R / −218.52 °Re) are flagged as invalid.