Rankine to Kelvin
Convert Rankine to kelvin — type a temperature in either box. The formula is K = °R × 5/9.
How to use
- Enter a temperature in the Rankine field.
- The Kelvin value updates instantly.
- Negative values work exactly the same way.
- Check the reference table for the fixed points.
Rankine to Kelvin formula
Temperature is the one conversion that needs more than a multiplication: the scales disagree about where zero sits, so an offset is required as well as a ratio.
K = °R × 5/9
Apply the offset first, then the ratio — reversing the order is the most common mistake.
Worked example
Converting 20 °R gives 11.11 K.
20 °R → 11.11 K
Reference points
Four temperatures worth memorizing, in both scales:
| Reference point | Rankine | Kelvin |
|---|---|---|
| water freezing | 491.67 °R | 273.15 K |
| a mild room | 527.67 °R | 293.15 K |
| body temperature | 558.27 °R | 310.15 K |
| water boiling | 671.67 °R | 373.15 K |
What is a degree Rankine?
Rankine is an absolute temperature scale that uses Fahrenheit-sized degrees, starting at absolute zero.
Definition: 0 °R is absolute zero and one degree Rankine equals one degree Fahrenheit, so °R = °F + 459.67.
Where it is used: US thermodynamics and aerospace engineering, where absolute temperature is needed but Fahrenheit degrees are the working convention.
What is a kelvin?
The kelvin is the SI base unit of thermodynamic temperature, counting from absolute zero rather than from a property of water.
Definition: Since 2019 defined by fixing the Boltzmann constant at exactly 1.380649×10⁻²³ joules per kelvin. Absolute zero is 0 K, which is −273.15 °C.
Where it is used: Physics and chemistry, color temperature of lighting, and astronomy.
Worth knowing: Written 'kelvin', not 'degrees kelvin', and the symbol K takes no degree sign.
Frequently asked questions
What is the formula to convert Rankine to kelvin?
Use K = °R × 5/9.
What is 0 °R in kelvin?
0 °R is 0 K.
What is 100 °R in kelvin?
100 °R is 55.56 K.
Does this work for negative temperatures?
Yes. The formula is linear, so it is valid above and below zero on either scale.
Is there anything to watch out for with kelvin?
Written 'kelvin', not 'degrees kelvin', and the symbol K takes no degree sign.