@thi.ng/units/units/temperature.js

Extensible SI unit creation, conversions, quantities & calculations (incl. ~170 predefined units & constants)

import { coherent, defUnit, unit } from "../unit.js";
const K = defUnit("K", "kelvin", coherent(4));
const celsius = defUnit("\u2103", "degree celsius", unit(4, 1, 273.15));
const fahrenheit = defUnit(
  "\u2109",
  "degree fahrenheit",
  unit(4, 1 / 1.8, 459.67 / 1.8)
);
export {
  K,
  celsius,
  fahrenheit
};