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Multiple conversions
To convert from degree Rankine (R) to degree Celsius (C), use the following formula:
C
= (R - 491.67) × 59
= R × 59 - 273.15
To convert from degree Rankine (R) to Kelvin (K), use the following formula:
K
= R × 59
To convert from degree Rankine (R) to degree Fahrenheit (F), use the following formula:
F
= R - 459.67
The Rankine scale (°R) is a temperature measurement system built on absolute zero, much like the Kelvin scale. However, Rankine is specifically designed to work with the Fahrenheit system. Think of it as the Fahrenheit version of Kelvin, used primarily by engineers in the United States.
The Rankine scale is an absolute temperature scale, meaning its starting point—0 °R—is absolute zero. This is the coldest possible temperature in the universe, where all atomic and molecular motion stops completely.
Unlike scales such as Celsius and Fahrenheit, which have arbitrary zero points, absolute scales begin at true zero. This distinction is vital in science and engineering, particularly when a calculation requires dividing one temperature by another.
Since Fahrenheit and Rankine share the same degree size, a change of 1°F is equivalent to a shift in 1°R.
To convert Fahrenheit (°F) to Rankine (°R), add 459.67 to the Fahrenheit value.
Formula: °R = °F + 459.67
Example: Water freezes at 32 °F. To find this on the Rankine scale, you would calculate: 32 + 459.67 = 491.67 °R
The Rankine scale is an absolute temperature scale that is comparable to the Kelvin scale. Its zero point, 0 °R, represents absolute zero, which is the theoretical temperature where all molecular movement comes to a halt.
Unlike relative scales such as Fahrenheit or Celsius, which have arbitrary zero points (like the freezing point of water), Rankine starts from a true fundamental zero.
You will almost exclusively find the Rankine scale in engineering and thermodynamics fields within the United States.
Many scientific laws, especially those related to gases and energy efficiency (such as the Ideal Gas Law), require an absolute temperature to yield accurate results.
Rankine allows engineers working with imperial units (feet, pounds, Fahrenheit) to perform these critical calculations without first converting everything to Kelvin, which is the absolute scale for the metric system. It streamlines their workflow by keeping all units consistent.
Rankine's arithmetic is deliberately simple, because it shares its degree size with Fahrenheit exactly as Kelvin shares its degree size with Celsius.
Two consequences follow. First, a difference of one degree Rankine and one degree Fahrenheit are the same interval, so any formula involving a temperature change can be carried between the scales untouched. Second, absolute zero is 0 °R = −459.67 °F, and water freezes at 491.67 °R.
By convention the scale is written without the degree sign in modern usage — 100 R, not 100 °R — matching the way Kelvin is written.