Kelvin to Rankine Converter — Convert K to °R (Exact: °R = K × 9/5)
Accurate Kelvin (K) to Rankine (°R) converter using the exact identity °R = K × 9/5. Ideal for thermodynamics, aerospace, power cycles, cryogenics, and U.S.-centric engineering documentation.
Exact identity: °R = K × 9/5. Explore more in our free temperature conversion tools hub.
About Kelvin to Rankine Conversion
Kelvin (K) and Rankine (°R) are both absolute temperature scales anchored at absolute zero, which makes them ideal for thermodynamics. Kelvin’s increments align with Celsius, while Rankine’s align with Fahrenheit. When U.S.-centric engineering teams or legacy standards expect Fahrenheit-style degree steps, converting K → °R provides absolute values in a familiar increment without changing the physical meaning of zero.
Kelvin to Rankine Formula
Exact relationship
Use the constant mapping between Celsius and Fahrenheit degree sizes:
°R = K × 9/5Examples:
273.15 K × 9/5 = 491.67 °R
300.00 K × 9/5 = 540.00 °RReverse calculation (°R → K)
Invert the transform to return to Kelvin:
K = °R × 5/9Related Temperature Converters
What is Kelvin?
Kelvin is the SI base unit for thermodynamic temperature. It positions absolute zero at 0 K and measures increments that correspond directly to energy changes. Scientists and engineers prefer Kelvin for calculations, models, and instrumentation because temperature differences in K translate naturally into thermodynamic relationships.
What is Rankine?
Rankine is an absolute scale using Fahrenheit-sized increments. It’s particularly relevant in U.S.-based thermodynamics, older aerospace documentation, and power-plant analysis where Fahrenheit conventions persist. °R behaves like Kelvin in being absolute (no negative absolute temperatures), but each degree is one Fahrenheit degree in size.
Step-by-Step: Converting K to °R
- Record the temperature in K.
- Multiply by 9/5 (or 1.8).
- Express the result in °R and round for display as needed.
Walkthrough examples:
Freezing point (absolute): 273.15 K → 491.67 °R
Room temperature: 293.15 K → 527.67 °R
Body temperature: 310.15 K → 558.27 °RCommon Conversions
Everyday checks for thermodynamics & aerospace
| K | °R |
|---|---|
| 0.00 | 0.00 |
| 77.00 | 138.60 |
| 273.15 | 491.67 |
| 293.15 | 527.67 |
| 298.15 | 536.67 |
| 373.15 | 671.67 |
Precision, Rounding & Significant Figures
Operational rounding
Choose display precision based on audience and instrument resolution: whole degrees for dashboards, one decimal for commissioning logs, two or more decimals for lab notebooks or model validation. Keep raw K values unrounded in storage, convert once at the pipeline boundary, and round at presentation time.
Consistent documentation
Standardize column names (e.g., temp_K, temp_R), avoid multi-stage conversions, and annotate reports with a short note such as: “Conversion uses °R = K × 9/5 (absolute scales with identical zero).” This prevents ambiguity for mixed audiences and future readers of your data.
Where This Converter Is Used
- 🛩️ Aerospace & propulsion: Cycle analysis, nozzle calculations, and performance curves documented in °R for U.S. teams.
- ⚙️ Power & energy: Brayton/Rankine cycle work, heat-rate reporting, and turbine performance comparisons.
- 🧪 Thermodynamics labs: Experiments that require absolute temperatures while presenting results in Fahrenheit-style increments.
- 🏭 Process & QA: Legacy SOPs and specs that historically adopted Fahrenheit/Rankine conventions.
- 🎓 Education: Courses explaining absolute scales and their relation to Celsius/Fahrenheit increments.
Quick Reference Table
| °R | K |
|---|---|
| 0.00 | 0.00 |
| 138.60 | 77.00 |
| 491.67 | 273.15 |
| 527.67 | 293.15 |
| 536.67 | 298.15 |
| 671.67 | 373.15 |
Frequently Asked Questions
What is the exact formula to convert Kelvin to Rankine?
Use °R = K × 9/5 (or 1.8 × K). Kelvin and Rankine share the same absolute zero, but their degree increments follow Celsius and Fahrenheit respectively. The factor 9/5 maps those increments exactly, so the transformation is linear and precise across the full range.
Why convert Kelvin to Rankine?
Rankine is an absolute temperature scale tied to Fahrenheit increments, widely used in U.S.-based thermodynamic analyses, power-plant and aerospace documentation, and older engineering literature. Converting K → °R lets you keep the benefits of absolute temperatures while presenting values in a Fahrenheit-aligned format for stakeholders who expect it.
Is Rankine written with a degree symbol?
Yes. Rankine uses the degree symbol (°R) because it inherits Fahrenheit-style degree increments. Kelvin, by contrast, omits the degree symbol entirely (e.g., 300 K, not 300 °K). Keeping notation consistent avoids confusion in specs, lab books, and code comments.
Does °R = 0 at the same point as K = 0?
Yes. Both Kelvin and Rankine are absolute scales with 0 at absolute zero. They differ only in the size of one degree: 1 K equals 1 °C, while 1 °R equals 1 °F. That’s why the conversion is a simple constant multiplier (9/5).
How do I convert Rankine back to Kelvin?
Use K = °R × 5/9. It’s the exact inverse of the forward relationship. In data pipelines, convert once at the boundary, store raw values with higher precision, and round only for display to prevent cumulative rounding drift.
Where is Rankine still common today?
You’ll still find Rankine in U.S.-centric thermodynamics textbooks, power-cycle calculations (Brayton/Rankine cycles), some aerospace documentation, and legacy code or standards that were originally built around Fahrenheit increments.
Is the conversion affected by negative temperatures?
No. Because both scales are absolute and share the same zero, the linear relationship holds for all values. Very low cryogenic temperatures in Kelvin convert linearly to Rankine the same way as room-temperature values do.
What precision should I use when reporting °R?
Match your instrument resolution and audience. Technical appendices often show one or two decimals; dashboards or executive summaries may prefer whole degrees. Store full precision internally, round at presentation time.
Can I convert K to °C first, then °C to °F, then add 459.67?
You can, but it’s more steps. The direct conversion °R = K × 9/5 is exact and avoids intermediate rounding. A common mental approximation is °R ≈ 1.8 × K.
Is Rankine used outside the U.S.?
Rarely. Most international work uses Kelvin (absolute) and Celsius (relative). Rankine persists mainly where Fahrenheit-based increments or legacy conventions still have operational value.
Tips for Working with K & °R
- Store high-precision Kelvin values and convert to °R only for display or report exports.
- Use consistent unit labels in plots, tables, and variable names to avoid mixing K, °C, °F, and °R.
- For mixed audiences, include both absolute (K/°R) and relative (°C/°F) scales where helpful, and explain why absolute temperature matters.
Popular Metric Conversion Tools
Reverse conversion
U.S. reporting
Thermodynamics
Legacy literature
Science & labs
DIY & apparel
Automotive & ballistics
Fuel & beverages
Fitness & freight
Global travel