The Kelvin to Rankine Calculator converts a Kelvin temperature into degrees Rankine, the Fahrenheit-sized absolute temperature scale. Enter a value in Kelvin, and the tool multiplies by 9/5, showing the substitution so the result can be verified without a separate reference chart.
Kelvin and Rankine are both absolute scales, meaning zero on either scale corresponds to the same physical point: absolute zero, where classical thermodynamic motion is at its theoretical minimum. Because both scales share that zero point, converting between them needs only a multiplication, with no offset to add or subtract.
Convert Kelvin to Rankine
To convert Kelvin to Rankine, multiply the Kelvin value by 9/5 (1.8).
°R = K × 9/5Worked example: convert 300 K to Rankine.
1. Multiply by 9/5. 300 × 1.8 = 540 °R.
So 300 K, a warm outdoor temperature, equals 540 °R. Because both scales start at zero for absolute zero, there is no offset to worry about, unlike every conversion pair that involves Celsius or Fahrenheit.
Understand why this pair is a pure scaling factor
Kelvin and Rankine are the two absolute temperature scales in common use. Both place zero at true absolute zero, the coldest theoretically possible temperature.
They differ only in the size of one degree: a Kelvin degree matches a Celsius degree in size, while a Rankine degree matches a Fahrenheit degree, and Fahrenheit degrees are smaller than Celsius degrees in a 5-to-9 ratio.
That is why multiplying by 9/5 is the entire conversion. No addition is needed because neither scale has a nonzero starting point to reconcile; the relationship is a straightforward proportional scaling, the same 9/5 factor that links Celsius-sized and Fahrenheit-sized degree changes everywhere else in this conversion family.
Check common reference points
| Kelvin | Rankine | Context |
|---|---|---|
| 0 K | 0 °R | Absolute zero |
| 273.15 K | 491.67 °R | Water freezes |
| 300 K | 540 °R | Warm outdoor temperature |
| 310.15 K | 558.27 °R | Average body temperature |
| 373.15 K | 671.67 °R | Water boils (sea level) |
Every Rankine value is the Kelvin value multiplied by exactly 1.8, and both scales agree at zero, since absolute zero is the shared reference point for the entire family.
Convert Rankine back to Kelvin
The Kelvin to Rankine Calculator also runs the reverse direction. To convert Rankine to Kelvin, divide by 9/5 (or multiply by 5/9).
K = °R × 5/9Worked example: convert 500 °R to Kelvin.
1. Multiply by 5/9. 500 × 5/9 ≈ 277.78 K.
Because there is no offset in either direction, dividing by 1.8 (or equivalently multiplying by 5/9) is the entire reverse calculation.
Use this pair in thermodynamic formulas
Physics and engineering formulas that depend on absolute temperature, such as the ideal gas law or radiation laws, require an absolute scale rather than a relative one like Celsius or Fahrenheit.
Scientists working in SI units default to Kelvin, while engineers working in Fahrenheit-based systems, particularly in some corners of US mechanical and aerospace engineering, use Rankine instead so they can keep Fahrenheit-sized degree readings while still satisfying the absolute-zero requirement of the underlying physics.
Because the two scales are proportional rather than offset, ratios of two Rankine temperatures equal the ratios of the corresponding Kelvin temperatures, which is a useful property when checking a calculation that involves a temperature ratio rather than a single absolute value.
Convert more Kelvin readings from real physical references
The same multiplication applies far outside the everyday range in the table above. Liquid nitrogen boils at about 77 K under normal atmospheric pressure, which converts to 77 × 1.8 = 138.6 °R. Dry ice sublimates at about 194.65 K, which converts to 194.65 × 1.8 = 350.37 °R.
Both of these cold reference points use the identical 9/5 scaling factor as the warm and body-temperature examples earlier on this page. Because Kelvin and Rankine share zero at absolute zero, the same multiplication holds whether the starting value sits near cryogenic temperatures or near everyday room temperature. No offset ever needs adding at either extreme, which keeps this particular conversion pair simpler than any pairing that involves Celsius or Fahrenheit directly.
Compare a solar-core estimate against everyday values
Extreme values on the Kelvin scale follow the same rule as room-temperature ones. An estimated core temperature of 15,000,000 K converts to 15,000,000 × 1.8 = 27,000,000 °R.
Placed next to the 138.6 °R figure for liquid nitrogen above, the comparison shows how the single multiplication factor scales cleanly across many orders of magnitude without ever needing a different formula for extreme temperatures.
Frequently asked questions
What is the formula to convert Kelvin to Rankine?
Multiply the Kelvin value by 9/5: °R = K × 9/5. For example, 300 K converts to 300 × 1.8 = 540 °R.
How do you convert Rankine back to Kelvin?
Multiply the Rankine value by 5/9: K = °R × 5/9. For example, 500 °R converts to 500 × 5/9 ≈ 277.78 K.
Why is there no addition or subtraction in this conversion?
Kelvin and Rankine both set zero at absolute zero, so they share the same starting point. Only the degree size differs, which means a single multiplication handles the entire conversion.
What is 0 K in Rankine?
0 K equals 0 °R, since both scales are anchored at absolute zero by definition.
What is water's freezing point in Kelvin and Rankine?
Water freezes at 273.15 K, which equals 491.67 °R.
Is Rankine used much outside engineering?
Rarely. Rankine appears mainly in specialised US engineering and thermodynamics contexts. Kelvin is the standard absolute scale in general scientific work worldwide.
Does this calculator also convert Celsius and Fahrenheit?
Yes. The same underlying engine powers the full Temperature Conversion Calculator, covering all four scales together with any source and target selectable directly.
Summary
Kelvin converts to Rankine with a single multiplication by 9/5, so 300 K becomes 540 °R and 273.15 K becomes 491.67 °R. Because both scales are anchored at absolute zero, no offset is needed in either direction; the reverse conversion multiplies by 5/9.
This makes Kelvin-to-Rankine the cleanest conversion in the temperature family, useful whenever a Fahrenheit-sized absolute reading is needed from a Kelvin measurement.