Fahrenheit to Rankine Converter
Type in either box. R = °F + 459.67 — same degree, absolute zero.
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The same degree, a different zero
Rankine is Fahrenheit's absolute scale. The degrees are exactly the same size; only the starting point moves, down to absolute zero. That makes this the simplest conversion in the set.
R = °F + 459.67
459.67 is how far below zero Fahrenheit absolute zero lies. Add it and every reading becomes positive, which is the entire point of an absolute scale: ratios start to mean something, and the temperature terms in thermodynamic formulas behave.
Rankine sits in the same relationship to Fahrenheit as kelvin does to Celsius. If you are comfortable with K = °C + 273.15, this is the same idea with different numbers.
The working, step by step
Every line updates with whatever you type above. Temperature is the one conversion where the method genuinely matters, because two things change at once: the size of a degree and the position of zero.
Why it is a line that misses the origin
Plotting one scale against the other shows the whole relationship at a glance. The slope is the size of a degree. The height at which the line crosses the vertical axis is the offset — the reason multiplying alone never works. Converting kilograms to pounds gives a line through (0, 0); this one does not.
The same temperature, two different numbers
One physical temperature, read off two scales. The tick marks are spaced differently and shifted along, which is exactly what the two numbers in the formula are doing.
Where does that sit?
A reading is easier to judge against temperatures you already know.
Your turn
Reading a method and being able to use it are different things. Answer within half a per cent and it counts as correct.
Score: 0 of 0
How to use this converter
- Type into either box. The other side updates as you go. There is no button to press.
- Negative readings are fine. Type a minus sign and the graph and scale below follow the value below zero.
- Swap the direction with the button between the boxes if you want to work the other way round.
- Set the decimals if the default is more or less precision than you need.
- Copy the answer with its unit, ready to paste.
- Share the result. The address bar tracks what you type, so the link you copy opens on the same reading.
If you enter something colder than absolute zero, the tool will say so rather than quietly converting a temperature that cannot exist.
Common uses and tips
Where this comes up
- American thermodynamics. Steam tables, gas-turbine work and combustion calculations published in US customary units use Rankine wherever absolute temperature is required.
- Aerospace and HVAC engineering in the United States, where the surrounding figures are all in Fahrenheit and switching to kelvin would mean converting everything else too.
- Textbook problems that give conditions in Fahrenheit and expect the ideal gas law to be applied — which it cannot be until the temperature is absolute.
Tips worth knowing
- Differences are identical. A 25 °F rise is a 25 R rise, because the degree size is unchanged.
- Rankine is written R or °R, and both are common. Kelvin, by contrast, never takes the degree sign.
- Rankine and kelvin relate by 1.8. R = K × 1.8, with no offset, because both start at absolute zero.
Readings people look up most
Each one opens the converter with the number already in it.
- -459.67 °F to R
- -40 °F to R
- 0 °F to R
- 32 °F to R
- 60 °F to R
- 68 °F to R
- 98.6 °F to R
- 212 °F to R
- 350 °F to R
- 1000 °F to R
Quick reference
| Fahrenheit | Rankine | Usually this is… |
|---|---|---|
| −459.67 °F | 0 R | absolute zero |
| −40 °F | 419.67 R | very cold |
| 0 °F | 459.67 R | home freezer |
| 32 °F | 491.67 R | water freezes |
| 68 °F | 527.67 R | room temperature |
| 98.6 °F | 558.27 R | body temperature |
| 212 °F | 671.67 R | water boils |
| 350 °F | 809.67 R | moderate oven |
Questions people ask
What is the formula for Fahrenheit to Rankine?
Add 459.67. The degrees are the same size on both scales, so nothing needs multiplying.
What is Rankine used for?
Absolute temperature in American engineering — thermodynamics, combustion, gas turbines — where the rest of the figures are in Fahrenheit.
How does Rankine relate to kelvin?
R = K × 1.8. Both start at absolute zero, so there is no offset between them, only the degree size.
Can Rankine be negative?
No. Like kelvin it starts at absolute zero, so a negative value means something has gone wrong.