Convert between Celsius, Fahrenheit and Kelvin.
Multiply the Celsius value by 1.8 and add 32: °F = °C × 1.8 + 32. The SI base unit of temperature is the kelvin, though everyday use in Latvia is Celsius. Twenty degrees Celsius is 68 Fahrenheit. Going back, subtract 32 and divide by 1.8. The two scales cross at −40 degrees, where both read the same.
The kelvin is the SI base unit of temperature and its scale starts at absolute zero. It is an absolute scale rather than one relative to a reference point, so the BIPM's SI Brochure writes 300 K rather than 300 °K. One kelvin step equals one degree Celsius.
The lowest possible temperature, where the thermal motion of particles reaches its minimum. It is 0 kelvin, or −273.15 degrees Celsius. The BIPM SI Brochure sets it as the origin of the kelvin scale. It cannot be reached in practice, only approached — laboratories have come within billionths of a degree, but never to it.
Because Fahrenheit built his scale on different reference points, not on water. He set zero by a salt-and-ice mixture and the upper point roughly by human body temperature. Water's freezing and boiling landing on 32 and 212 was incidental. SI does not use the Fahrenheit scale at all.