Temperature Converter Tools – Convert °C, °F, K & Rankine (°R)
Welcome to the temperature conversion hub—your one place to convert between Celsius (°C), Fahrenheit (°F), Kelvin (K), and Rankine (°R). Every calculator uses exact relationships with instant results and a consistent, mobile-first interface.
Whether you’re preparing lab reports, building weather dashboards, calibrating sensors, or teaching thermodynamics, precise conversions matter. We derive all formulas from internationally defined offsets and scale factors, compute with full precision, and recommend rounding once at output so your charts, PDFs, and CSV exports stay in agreement.
For robust analytics, store a canonical unit—Kelvin is the SI base unit—and convert to °C, °F, or °R for UI and regional expectations. Each page below includes the exact equation, step-by-step examples, best-practice rounding, and guidance for avoiding common pitfalls.
Celsius to Fahrenheit
°F = (°C × 9/5) + 32 (exact).
Fahrenheit to Celsius
°C = (°F − 32) × 5/9 (exact).
Celsius to Kelvin
K = °C + 273.15 (exact offset).
Kelvin to Celsius
°C = K − 273.15 (exact offset).
Fahrenheit to Kelvin
K = (°F + 459.67) × 5/9 (exact).
Kelvin to Fahrenheit
°F = K × 9/5 − 459.67 (exact).
Celsius to Rankine
°R = (°C + 273.15) × 9/5 (exact).
Rankine to Celsius
°C = (°R − 491.67) × 5/9 (exact).
Fahrenheit to Rankine
°R = °F + 459.67 (exact offset).
Rankine to Fahrenheit
°F = °R − 459.67 (exact offset).
Kelvin to Rankine
°R = K × 9/5 (exact).
Rankine to Kelvin
K = °R × 5/9 (exact).
Why Exact Temperature Conversions Matter
Temperature calculations combine both scale (the size of a degree) and offset (the zero point). Mixing these incorrectly causes systematic errors—e.g., averaging Fahrenheit directly with Celsius without first converting to a common base. By using the fixed offsets 273.15 and 459.67 and the exact scale factors 9/5 and 5/9, you avoid drift across sensors, apps, and exports.
Core Relationships You’ll Use Daily
-
K = °C + 273.15•°C = K − 273.15(exact) -
°R = °F + 459.67•°F = °R − 459.67(exact) -
°F = (°C × 9/5) + 32•°C = (°F − 32) × 5/9(exact) -
K = (°F + 459.67) × 5/9•°F = K × 9/5 − 459.67(exact) °R = K × 9/5•K = °R × 5/9(exact)- Absolute zero:
0 K = −273.15 °C = −459.67 °F = 0 °R
Rounding, Precision & Display Strategy
Keep internal precision high—especially when averaging many sensor readings or aggregating over time. Consumer UIs often use whole degrees; scientific contexts use one or two decimals matching instrument specs. Round once at presentation or export to keep dashboards, PDFs, and emails consistent.
Data Modeling & Developer Tips
Normalize to Kelvin in storage (temp_K) and derive temp_C, temp_F, or temp_R for UI. Centralize conversion utilities and maintain a regression set of known points (freezing and boiling of water, standard room temperature). Validate in CI in both directions to catch accidental constant changes or formatting issues.
Regional Conventions & Accessibility
Most of the world uses Celsius for weather and household contexts; the US typically uses Fahrenheit. Scientific and engineering workflows favor Kelvin. Present the unit your audience expects while keeping Kelvin canonical. Label units in headers and ensure strong color contrast so values remain readable in all modes.
Common Use Cases
- Weather and HVAC dashboards (°C/°F UI, Kelvin for analytics)
- Laboratory and industrial process control (Kelvin or Rankine in thermodynamic equations)
- Education (teaching offsets, absolute zero, and scale factors across all four systems)
- APIs & data feeds (normalize to K; present locale-aware °C/°F on clients)
Worked Examples
Weather card: 18 °C → °F = (18 × 9/5) + 32 = 64.4 °F. In Kelvin: 18 + 273.15 = 291.15 K. Store 291.15 K, render 18 °C or 64.4 °F depending on locale.
Process control: 750 °R → K = 750 × 5/9 = 416.666… K. In °C that’s 143.516… °C. Keep the exact value in K for calculations; round to 143.52 °C for printouts per your QA policy.
Sensor pipeline: A probe logs 300.00 K. In °C: 26.85 °C; in °F: 80.33 °F. Average readings in Kelvin, then convert for display to avoid bias introduced by offsets.
Frequently Asked Questions
What are the exact relationships among °C, °F, K, and Rankine (°R)?
Kelvin and Celsius share an exact offset: K = °C + 273.15 and °C = K − 273.15. Fahrenheit and Rankine also share an exact offset: °R = °F + 459.67 and °F = °R − 459.67. Scale factors between Kelvin/Celsius and Fahrenheit/Rankine are exact 9/5 and 5/9. From these follow the standard formulas: °F = (°C × 9/5) + 32, °C = (°F − 32) × 5/9, K = (°F + 459.67) × 5/9, and °R = K × 9/5.
Which temperature unit should I store as canonical in my system?
Kelvin is the SI base unit and is ideal for storage, physics calculations, and analytics because it is absolute (no negative values above absolute zero). For consumer surfaces, convert to °C or °F at the edges. Document this policy so every API and export applies the same math.
What is absolute zero and why does it matter for conversions?
Absolute zero is 0 K (−273.15 °C, −459.67 °F, 0 °R), the theoretical minimum temperature where thermal motion is minimized. Converters should never produce temperatures below absolute zero. If user input implies that, show validation or domain-specific messaging.
Why do scientists prefer Kelvin while weather apps use °C/°F?
Kelvin simplifies thermodynamic equations and eliminates negative values for many computations. Weather apps present °C or °F because those scales are familiar to the public. A best practice is to store K in your database and render in °C or °F for UI depending on locale.
How should I round temperatures for dashboards and printouts?
Compute with full precision internally and round once on display or export. Weather and consumer UIs often use whole °C/°F or one decimal; lab data may require two or more decimals, matching instrument resolution. Declare your rounding rule in a short methods note.
What is Rankine and where is it used?
Rankine (°R) is an absolute scale like Kelvin but sized in Fahrenheit degrees. It is used in some thermodynamics and aerospace contexts, especially in the US. Conversions are straightforward: °R = K × 9/5 and K = °R × 5/9, with °F offsets via ±459.67.
Do the constants 273.15 and 459.67 ever change?
These offsets are fixed by international agreement and are treated as exact in engineering and science. While the kelvin was redefined in 2019 using the Boltzmann constant, the practical conversion offsets used here remain stable and exact for calculations.
Any pitfalls when mixing user input, logs, and exports?
Common issues include double-rounding, mixing units within a single column, and forgetting the offsets in °C/°F conversions. Normalize to a canonical unit (K), convert once for UI, and label table headers with explicit units (e.g., temp_K, temp_C).
How do I validate my conversion pipeline automatically?
Create a small regression set of known pairs—like 0 °C = 273.15 K = 32 °F = 491.67 °R; 100 °C = 212 °F = 373.15 K—and assert both directions in CI. This catches formatting mistakes and accidental edits to constants.
What about precision for sensors and IoT devices?
Keep the raw sensor precision in Kelvin (or °C) as reported, then round for UI. If you average many readings, average in the canonical unit first, then convert and round once at presentation to avoid bias.
Keep This Page Handy
Bookmark this category page for rapid access to every temperature converter on MetricCalc. New tools will follow the same layout and rounding philosophy so you can move across unit systems without friction. If a pair is missing, tell us and we’ll add it to the library with the same exacting standards.