Kelvin to Celsius Converter — Convert K to °C (Exact: °C = K − 273.15)
High-accuracy Kelvin (K) to Celsius (°C) converter using the exact identity °C = K − 273.15. Ideal for thermodynamics, chemistry, materials science, HVAC modeling, labs, and education.
Exact identity: °C = K − 273.15. Explore more in our temperature conversion tools hub.
About Kelvin to Celsius Conversion
Kelvin (K) is the SI base unit for thermodynamic temperature and starts at absolute zero. Celsius (°C) uses the same increment size but is offset so that water freezes at 0 °C and boils at 100 °C at 1 atm. Converting K → °C translates absolute measurements into a format that most readers recognize instantly—perfect for reports, dashboards, and non-technical documentation.
Kelvin to Celsius Formula
Exact relationship
Shift by the absolute-zero offset:
°C = K − 273.15Examples:
273.15 K → 0.00 °C
298.15 K → 25.00 °C
373.15 K → 100.00 °CReverse calculation (°C → K)
Invert to return to Kelvin:
K = °C + 273.15Related Temperature Converters
What is Kelvin?
Kelvin is absolute: 0 K represents the theoretical minimum of thermal energy. The degree size matches Celsius, which makes differences interchangeable (ΔK = Δ°C). Scientists model in Kelvin to keep equations straightforward and unit-consistent.
What is Celsius?
Celsius anchors to water’s phase changes at standard pressure and is the default for everyday communication—weather updates, recipes, and many engineering setpoints. Converting back to °C helps non-specialists grasp results quickly without losing technical rigor.
Step-by-Step: Converting K to °C
- Record the temperature in K.
- Subtract 273.15 to align with the Celsius scale.
- Report the result in °C; round only for display.
Walkthrough examples:
Cold room: 263.15 K → -10.00 °C
Room temperature: 294.15 K → 21.00 °C
Boiling water: 373.15 K → 100.00 °CCommon Conversions
Everyday checks for labs, HVAC & education
| 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 |
Precision, Rounding & Significant Figures
Operational rounding
Use whole degrees or one decimal for high-level dashboards; keep one to two decimals for commissioning; and two or more for lab work. Retain unrounded values internally and round only at presentation to prevent drift in downstream analytics.
Consistent documentation
Name variables predictably (e.g., temp_K, temp_C), convert once at the pipeline edge, and include a short note such as: “Conversion uses °C = K − 273.15; inverse K = °C + 273.15.” This reduces ambiguity in mixed audiences.
Where This Converter Is Used
- ⚗️ Thermodynamics & physical chemistry: Gas laws, calorimetry, EOS models—computed in Kelvin, reported in °C.
- 🧪 Materials & cryogenics: Presenting absolute measurements in an audience-friendly °C for quick interpretation.
- 🏭 Process engineering & HVAC: Controls in Kelvin; operating setpoints and SOPs in Celsius for technicians.
- 🎓 Education & labs: Teaching absolute temperature while letting students interpret in °C.
- 🛰️ Aerospace & spaceflight: Instrument calibration in Kelvin with parallel °C reporting for stakeholders.
Quick Reference Table
| °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 |
Frequently Asked Questions
What is the exact formula to convert Kelvin to Celsius?
Use °C = K − 273.15. Kelvin is an absolute scale with its zero at absolute zero, and Celsius shares the same degree size but is offset by 273.15. Subtracting 273.15 moves a Kelvin value back onto the Celsius scale exactly—no approximations needed.
Why do scientists calculate in Kelvin but publish in Celsius?
Equations for energy, gas laws, and radiation assume an absolute temperature. Kelvin eliminates hidden offsets, making math simpler and less error-prone. Results are then presented in Celsius for readability because °C is familiar to most audiences (weather, cooking, setpoints).
Can I convert via Fahrenheit or Rankine first?
You can, but it’s unnecessary. The direct mapping °C = K − 273.15 is exact and avoids chain-rounding. If you also need °F or °R outputs, compute them in parallel from the same Kelvin input to keep pipelines clean and reproducible.
How do I convert Celsius back to Kelvin?
Use the inverse: K = °C + 273.15. In software and spreadsheets, convert once at the boundary, store full-precision values, and apply rounding only at presentation to prevent cumulative error across transformations.
Is this conversion valid at cryogenic temperatures?
Yes. The mapping is linear over the entire range, including very low temperatures. In cryogenics and materials labs, align display precision with sensor resolution so small but meaningful differences aren’t lost.
Do temperature differences transform cleanly between K and °C?
Yes. Because the degree size is identical, ΔK = Δ°C. Only absolute readings involve the +/− 273.15 offset. Differences (deltas) are interchangeable between K and °C.
What precision should I display for Celsius?
Match audience and instrumentation: dashboards often use whole degrees or one decimal; commissioning logs and lab notebooks may justify two or more. Keep raw values unrounded in storage and round at render time.
How can I sanity-check a spreadsheet or ETL job?
Use anchors: 0 °C ↔ 273.15 K; 25 °C ↔ 298.15 K; 100 °C ↔ 373.15 K. If outputs differ, confirm constants (273.15, not 273), order of operations, unit labels, and that you’re rounding at the end—not in the middle.
Does Kelvin use a degree symbol?
No. Kelvin is written as K (e.g., 298.15 K). Reserve the degree symbol for Celsius (°C), Fahrenheit (°F), and Rankine (°R). Consistent notation prevents confusion in plots, tables, and code comments.
When is it acceptable to keep results in Kelvin?
When collaborating with technical teams, publishing thermodynamic analyses, or configuring models and simulations, Kelvin communicates absolute context and avoids ambiguity. For general audiences, mirror results in °C alongside K for clarity.
Tips for Working with K & °C
- Compute in Kelvin; present in °C with clear labels for non-technical readers.
- Convert once at system boundaries, keep full precision internally, and round only at presentation.
- Document constants and rounding policy in a short footnote or API doc for reproducibility.
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