Fahrenheit to Rankine
The Rankine scale (°Ra, sometimes °R) is the absolute-temperature counterpart of Fahrenheit, used mainly in US engineering and thermodynamics where calculations need a zero point at absolute zero. This converter changes Fahrenheit (°F) into Rankine and back in one place — handy for gas-law, combustion and heat-transfer work.
How it works
Rankine uses exactly the same degree size as Fahrenheit but shifts the zero point down to absolute zero, the coldest temperature physically possible. Because of that, conversion is a simple additive offset:
°Ra = °F + 459.67 (and the reverse, °F = °Ra − 459.67)
There is no scaling factor — only the 459.67 shift that separates the Fahrenheit zero from absolute zero. Type into either field and the other updates instantly, in both directions.
Where the 459.67 constant comes from
Absolute zero is the temperature at which all thermal motion stops and no energy can be extracted from a system. It falls at −273.15 °C, which in Fahrenheit is −459.67 °F. Because the Rankine scale starts at this physical minimum and uses the same degree size as Fahrenheit, the only operation needed is adding that 459.67 offset. The Kelvin scale does the same thing for Celsius (adding 273.15), which is why 0 K = 0 °Ra.
Reference table
| Fahrenheit (°F) | Rankine (°Ra) | What this represents |
|---|---|---|
| −459.67 °F | 0 °Ra | Absolute zero |
| −40 °F | 419.67 °Ra | Where °F and °C are equal |
| 0 °F | 459.67 °Ra | Fahrenheit zero |
| 32 °F | 491.67 °Ra | Freezing point of water |
| 98.6 °F | 558.27 °Ra | Human body temperature |
| 212 °F | 671.67 °Ra | Boiling point of water |
| 1000 °F | 1459.67 °Ra | Typical industrial combustion range |
When engineers use Rankine
The Rankine scale appears in US thermodynamics and mechanical engineering contexts where working in Fahrenheit-sized degrees is natural but an absolute zero reference is required. It is most common in:
- Ideal gas law calculations: The ideal gas law PV = nRT requires an absolute temperature (T cannot be negative or zero in the formula). When pressures and temperatures are given in customary US units (psia, Fahrenheit), converting to Rankine lets engineers apply the law without switching to SI units.
- Thermodynamic efficiency: Carnot efficiency calculations compare absolute temperatures of the hot and cold reservoirs. Rankine keeps those temperatures in the US unit system.
- Aviation and aerospace: Some US aerospace engineering standards still express temperatures in Rankine, particularly in older reference documents and textbooks.
- Combustion engineering: Flame temperatures, adiabatic flame temperature calculations, and heat-transfer problems in US-based industrial settings often appear in Rankine.
The key practical note is that Rankine is only used in the United States, and primarily in engineering documents. Scientific and international work overwhelmingly uses Kelvin.
Every conversion runs entirely in your browser — no data is ever uploaded.