🌡️ °R to K — Rankine to Kelvin Converter

Unlike multi-unit dashboards, this tool is built around one job: Rankine (r) into Kelvin (k), with reference values for this exact pair. Bookmark it if you convert r to k often — the layout stays the same so you can re-run values quickly. Common in cooking, weather, lab work, HVAC, and manufacturing.

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Formula K = °R × 5/9

All Rankine conversions

Unit	Name	Value
°C	Celsius	-272.59444
°F	Fahrenheit	-458.67
K	Kelvin	0.55555556

Related Temperature conversions

°C → °F °F → °C °C → K K → °C °F → K

⚡ How to Convert Rankine to Kelvin

Multiply by 5/9 (≈ 0.5556). Formula: K = °R × 5/9. Example: 540°R × 5/9 = 300 K. Reverse: °R = K × 9/5.

Worked Examples

Example 1 — Converting US legacy table to SI calculation

671.67°R × 5/9 = 373.15 K

An older American steam table lists a boiler temperature as 671.67°R. An engineer applying the Clausius-Clapeyron equation (which requires Kelvin) converts to 373.15 K — the boiling point of water — to calculate vapour pressure correctly.

Example 2 — Aerospace — converting NASA spec to SI

2880°R × 5/9 = 1600 K

A NASA legacy document specifies turbine inlet temperature as 2880°R. A European aerospace supplier must verify this against their own specifications in Kelvin — it converts to 1600 K, within the operating range of modern single-crystal turbine blades.

Example 3 — Cryogenics — US liquid hydrogen spec to Kelvin

36.5°R × 5/9 = 20.28 K

A US aerospace component datasheet specifies liquid hydrogen storage at 36.5°R. Scientists applying quantum thermodynamic models (which require Kelvin) convert to 20.28 K — the boiling point of LH₂ used in rocket propellant calculations.

Example 4 — Process engineering — converting Rankine output

900°R × 5/9 = 500 K

A legacy US process simulation outputs reactor temperature as 900°R. The engineer converts to 500 K to use in a modern kinetics model that requires SI units, ensuring the activation energy calculation is correctly performed.

Rankine to Kelvin — Reference Table

Rankine (°R)	Kelvin (K)	Real-world context
0°R	0 K	Absolute zero — both scales start here
138.87°R	77.15 K	Liquid nitrogen boiling point
491.67°R	273.15 K	Water freezing point
536.67°R	298.15 K	Standard thermodynamic reference (25°C)
558.27°R	310.15 K	Human body temperature
671.67°R	373.15 K	Water boiling point
1800°R	1000 K	Industrial furnace range
10400.4°R	5778 K	Surface of the Sun

Mental Math Tricks for °R ↔ K

Divide by 1.8 — that's it

°R ÷ 1.8 = K. Both start at zero. 540°R ÷ 1.8 = 300 K. No offset constant needed.

Reverse: multiply by 1.8

K × 1.8 = °R. 300 K × 1.8 = 540°R.

Anchor: 540°R = 300 K

A convenient round-number anchor. Scale proportionally — every 18°R = 10 K.

No offset — unlike all other conversions

Fahrenheit↔Celsius needs ±32. Celsius↔Kelvin needs ±273.15. But Rankine↔Kelvin needs only a multiplication — the simplest temperature conversion between different scales.

Who Uses This Conversion?

Real professions and situations that need °R to K conversion

🔬

Scientists Receiving US Engineering Data

When US engineering partners or contractors provide temperatures in Rankine, scientists applying thermodynamic equations (which universally require Kelvin) must convert before any calculation.

🏭

International Engineers Using US Software

Engineers outside the US working with American process simulation software (Aspen, HYSYS with Rankine settings) extract Rankine outputs and convert to Kelvin for their SI-based calculations and reports.

🎓

International Students Using US Textbooks

Engineering students from Europe, Asia or Australia studying with American thermodynamics textbooks encounter Rankine in examples. Converting to Kelvin validates answers against their SI-based lecture notes.

✈️

European Aerospace Suppliers to US Primes

Airbus, Rolls-Royce, Safran and other European suppliers receiving Boeing or Lockheed thermal specs in Rankine convert to Kelvin for their own design and analysis tools, all of which use SI units.

📐

SI Standards Harmonisation Engineers

Engineers converting ASME/API standards (which may use Rankine) to ISO/EN equivalents (Kelvin) for international product certification must perform this conversion for every temperature reference in the documents.

💡

Energy Research Scientists

Researchers analysing US energy efficiency data — often published in BTU-per-hour and Rankine — convert to SI units (watts and Kelvin) for publication in international journals and comparison with global datasets.

All Rankine Conversions

Why this Rankine to Kelvin page is different

Below, FAQs and examples stay locked to r → k so search engines and readers get pair-specific guidance—not a reused template with names swapped.

Pair-specific questions (r to k)

Use this r-to-k page when you already know both units and want a fast, focused answer with examples for Rankine and Kelvin. It is especially handy for cooking, weather, lab work, HVAC, and manufacturing, where this pair appears repeatedly.

No — Rankine (r) and Kelvin (k) measure the same kind of quantity but on different scales. Always convert with the correct factor before plugging values into equations or specs.

The live converter shows high-precision results and you can copy what you need. For official documents, round Rankine/Kelvin values to the precision your standard or client requires.

Frequently Asked Questions

Multiply by 5/9: K = °R × 5/9. Example: 540°R × 5/9 = 300 K.

0°R equals 0 K — both scales start at absolute zero. No offset is needed for this conversion.

491.67°R equals 273.15 K — the freezing point of water.

671.67°R equals 373.15 K — the boiling point of water.

Because both Rankine and Kelvin start at absolute zero. There is no additive offset — just a multiplicative factor of 5/9. This makes it the simplest of all cross-scale temperature conversions.

536.67°R equals 298.15 K — the standard thermodynamic reference temperature (25°C).

1°R equals 5/9 K ≈ 0.5556 K. The Rankine degree is smaller than the Kelvin because Fahrenheit degrees are smaller than Celsius degrees.

About Rankine and Kelvin

Rankine (°R)

The Rankine scale (symbol: °R) was proposed by William John Macquorn Rankine in 1859 as an absolute temperature scale using Fahrenheit degree intervals. Starting at absolute zero (0°R = 0 K), it provides an absolute reference without requiring the −273.15 offset of Celsius-to-Kelvin conversion.

Used primarily in US engineering thermodynamics, Rankine remains in legacy aerospace documentation, chemical engineering software and ASME standards. Rankine was a professor at the University of Glasgow and one of the founders of thermodynamics, also known for developing the Rankine cycle — the theoretical basis of steam power plants.

Kelvin (K)

The Kelvin (symbol: K) is the SI base unit of thermodynamic temperature, universally used in science and international engineering. Starting at absolute zero, it shares degree intervals with Celsius (0°C = 273.15 K). No degree symbol is used — write 300 K, not 300°K.

Defined since 2019 by the Boltzmann constant (k = 1.380649×10⁻²³ J/K), the Kelvin is the primary absolute temperature scale worldwide. All major thermodynamic equations (ideal gas law, Stefan-Boltzmann, Arrhenius) require temperature in Kelvin. The scale was named after Lord Kelvin by decision of the CGPM in 1954.

Common use: Rankine-to-Kelvin conversion is needed when bringing US engineering data into SI-based scientific calculations. The absence of any additive offset (just multiply by 5/9) makes this the most mathematically elegant of all temperature scale conversions.