Temperature Converters

Temperature is a scalar physical quantity expressing the thermal energy or "hotness" of a substance. It is one of the seven SI base quantities; the kelvin (K) is the SI base unit, defined since 2019 by fixing the Boltzmann constant. In everyday life, Celsius dominates most of the world for weather, cooking, and medicine, while Fahrenheit remains the standard in the United States. Absolute scales — kelvin and Rankine — are essential in thermodynamics and engineering, where calculations require a true zero. Several historical scales (Newton, Réaumur, Rømer, Delisle) were proposed in the early 18th century before Celsius and Fahrenheit became standard. Temperature converts non-linearly between scales because most scales have both different zero points and different degree sizes.