Celsius to Kelvin Converter — Convert °C to K (Exact: K = °C + 273.15)
High-accuracy Celsius (°C) to Kelvin (K) converter using the exact identity K = °C + 273.15. Ideal for thermodynamics, chemistry, materials science, HVAC modeling, and education.
Exact identity: K = °C + 273.15. Explore more in our free temperature metric converter tools hub.
About Celsius to Kelvin Conversion
Celsius (°C) is the day-to-day unit for weather, lab notes, and engineering setpoints across most of the world. Kelvin (K) is the SI base unit for thermodynamic temperature. Converting °C → K moves from a relative scale tied to water’s phase-change points to an absolute scale anchored at absolute zero—perfect for equations involving energy and state variables.
Celsius to Kelvin Formula
Exact relationship
Shift by the absolute-zero offset:
K = °C + 273.15Examples:
0.00 °C → 273.15 K
25.00 °C → 298.15 K
100.00 °C → 373.15 KReverse calculation (K → °C)
Invert to return to Celsius:
°C = K − 273.15Related Temperature Converters
What is Celsius?
Celsius sets 0 °C at the freezing point and 100 °C at the boiling point of water at 1 atm. It’s intuitive for everyday use and remains the preferred display unit for weather services, cooking, and many engineering dashboards—especially when communicating with non-specialists.
What is Kelvin?
Kelvin is absolute: 0 K is absolute zero. A 1-degree change in Kelvin equals a 1-degree change in Celsius (ΔK = Δ°C), which simplifies calculations and makes deltas interchangeable. Most scientific modeling and publication standards use Kelvin as the canonical temperature unit.
Step-by-Step: Converting °C to K
- Record the temperature in °C.
- Add 273.15 to shift to the absolute Kelvin scale.
- Report the result in K; round only for display.
Walkthrough examples:
Room temperature: 21.00 °C → 294.15 K
Body temperature: 37.00 °C → 310.15 K
Boiling water: 100.00 °C → 373.15 KCommon Conversions
Everyday checks for labs, HVAC & education
| °C | K |
|---|---|
| -40.00 | 233.15 |
| 0.00 | 273.15 |
| 20.00 | 293.15 |
| 25.00 | 298.15 |
| 37.00 | 310.15 |
| 100.00 | 373.15 |
Precision, Rounding & Significant Figures
Operational rounding
For dashboards, whole K or one decimal is common. Commissioning logs may keep one decimal; lab notebooks often justify two or more. The key is to store unrounded values and apply rounding only when rendering the final result to users.
Consistent documentation
Standardize variable names (e.g., temp_C, temp_K), convert once at the pipeline boundary, and avoid repeated back-and-forth transforms. Add a methods note like: “Conversion uses K = °C + 273.15; inverse °C = K − 273.15.” It reduces ambiguity in mixed audiences.
Where This Converter Is Used
- ⚗️ Thermodynamics & physical chemistry: Gas laws, reaction kinetics, and calorimetry on an absolute scale.
- 🧪 Materials & cryogenics: Low-temperature phenomena tracked with high-precision Kelvin readings.
- 🏭 Process engineering & HVAC: Modeling and controls where setpoints are computed in Kelvin and displayed in °C.
- 🎓 Education & labs: Teaching absolute temperature concepts, state variables, and unit systems.
- 🛰️ Aerospace & spaceflight: Instrument calibration, thermal balance, and radiation calculations in Kelvin.
Quick Reference Table
| K | °C |
|---|---|
| 233.15 | -40.00 |
| 273.15 | 0.00 |
| 293.15 | 20.00 |
| 298.15 | 25.00 |
| 310.15 | 37.00 |
| 373.15 | 100.00 |
Frequently Asked Questions
What is the exact formula to convert Celsius to Kelvin?
Use K = °C + 273.15. This shifts the relative Celsius scale onto the absolute Kelvin scale by adding a constant offset of 273.15. The relationship is linear and exact across all temperatures, from cryogenic to high-temperature applications.
Why does science prefer Kelvin for calculations?
Kelvin is an absolute scale starting at absolute zero, so equations for energy, gas laws, and radiation work without hidden offsets. Using Kelvin prevents mistakes that can arise when plugging Celsius directly into thermodynamic formulas.
Can I convert via Fahrenheit or Rankine first?
You could, but it adds unnecessary steps. For °C → K, the direct formula K = °C + 273.15 is exact and simplest. If you also need °F or °R outputs, compute them in parallel from Kelvin to avoid chain-rounding.
How do I convert Kelvin back to Celsius?
Use the inverse: °C = K − 273.15. In data pipelines, convert once at the boundary, store values at full precision, and round only for display to prevent cumulative rounding drift.
What precision should I display for Kelvin?
Match your sensor resolution and your audience. Dashboards might use whole Kelvin or one decimal; commissioning logs and lab notebooks often justify two or more decimals. Keep raw values unrounded in storage and round only at presentation time.
Is the conversion valid at cryogenic temperatures?
Yes. Because Kelvin is absolute and the mapping from Celsius is linear (add 273.15), it remains valid down to very low temperatures. In cryogenics and materials work, align rounding with instrument resolution to preserve small but meaningful deltas.
Do temperature differences convert cleanly between °C and K?
Yes. Differences are identical because the degree size is the same: ΔK = Δ°C. Only absolute readings involve the +273.15 offset; deltas do not.
How can I sanity-check a spreadsheet or ETL job?
Anchor points: 0 °C → 273.15 K; 100 °C → 373.15 K; 25 °C → 298.15 K. If outputs deviate, confirm you added 273.15 (not 273) and that rounding happens at the end of the pipeline.
When should I still present results in Celsius?
Present in Celsius for public-facing charts, operating manuals, or non-technical readers. Do the math in Kelvin, then include Celsius for readability. Clear unit labels prevent confusion.
Does Kelvin use a degree symbol?
No—the unit is written as K (e.g., 298.15 K). Reserve the degree symbol for Celsius (°C), Fahrenheit (°F), and Rankine (°R).
Tips for Working with °C & K
- Do the math in Kelvin; present in °C for broad audiences with clear labels and units.
- Convert once at system boundaries, keep full precision internally, and round only at presentation time.
- Document your constants in footnotes or API docs to keep analyses reproducible.
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