8th  Top scientific units named after people 
from Rankine  to Rankine  

Celsius  [°C] = ([°R] − 491.67) × ^{5}⁄_{9}  [°R] = ([°C] + 273.15) × ^{9}⁄_{5} 
Fahrenheit  [°F] = [°R] − 459.67  [°R] = [°F] + 459.67 
Kelvin  [K] = [°R] × ^{5}⁄_{9}  [°R] = [K] × ^{9}⁄_{5} 
For temperature intervals
rather than specific temperatures, 1 R = 1 °F = ^{5}⁄_{9} °C = ^{5}⁄_{9} K Comparisons among various temperature scales 
Rankine is a thermodynamic (absolute) temperature scale named after the Scottish engineer and physicist William John Macquorn Rankine, who proposed it in 1859.
The symbol for degrees Rankine is °R^{[1]} (or °Ra if necessary to distinguish it from the Rømer and Réaumur scales). Zero on both the Kelvin and Rankine scales is absolute zero, but the Rankine degree is defined as equal to one degree Fahrenheit, rather than the one degree Celsius used by the Kelvin scale. A temperature of −459.67 °F is exactly equal to 0 °R.
Some engineering fields in the U.S. measure thermodynamic temperature using the Rankine scale.^{[2]} However, throughout the scientific world and many times even in United States engineering, thermodynamic temperature is measured in kelvins.^{[2]} The US National Institute of Standards and Technology does not recommend using degrees Rankine in NIST publications.^{[1]}
Some key temperatures relating the Rankine scale to other temperature scales are shown in the table below.
Kelvin  Celsius  Fahrenheit  Rankine  

Absolute zero (by definition) 
0 K  −273.15 °C  −459.67 °F  0 °R 
Freezing point of water^{[3]}  273.15 K  0 °C  32 °F  491.67 °R 
Triple point
of water (by definition) 
273.16 K  0.01 °C  32.018 °F  491.688 °R 
Boiling point of water^{[4]}  373.1339 K  99.9839 °C  211.9710 °F  671.641 °R 

The Rankine scale is a thermodynamic (absolute) temperature scale. It is based around absolute zero. Rankine is similar to the Kelvin scale in that it starts at absolute zero and 0°Ra is the same as 0K but is different as a change of 1°Ra is the same as a change of 1°F (Fahrenheit) and not 1°C (Celsius). Note that the abbreviation °R is ambiguous, as it can also refer to the Réaumur scale.
The Kelvin and Rankine temperature scales are defined so that absolute zero is 0 kelvins (K) or 0 degrees Rankine (°R). The Celsius and Fahrenheit scales are defined so that absolute zero is −273.15 °C or −459.67 °F.
The Rankine scale was originally used in the United States.
