Updated September 2026
Celsius to Kelvin
Instantly convert celsius to kelvin with fast, accurate, real-time results.
Contents
The Kelvin scale is the SI base unit for thermodynamic temperature, used in physics, chemistry, astronomy, and engineering. Converting Celsius to Kelvin is straightforward — this °C to K converter does it instantly. For the reverse, see our Kelvin to Celsius converter. To convert to Fahrenheit, see Celsius to Fahrenheit.
The °C to K Formula
The Celsius and Kelvin scales have the same degree size — one kelvin equals one Celsius degree. They differ only by their zero points: 0 K is absolute zero (the coldest possible temperature), while 0°C is the freezing point of water.
Example: 25°C + 273.15 = 298.15 K
The exact offset is 273.15, based on the International Temperature Scale (ITS-90) definition. For most practical purposes, 273 is accurate enough; for scientific work, always use 273.15.
Key Temperature Reference Points (°C to K)
| °C | K | What it is |
|---|---|---|
| −273.15°C | 0 K | Absolute zero — coldest possible temperature |
| −269.15°C | 4 K | Boiling point of helium (at 1 atm) |
| −195.79°C | 77.36 K | Boiling point of liquid nitrogen |
| −183.0°C | 90.15 K | Boiling point of liquid oxygen |
| −78.5°C | 194.65 K | Sublimation point of dry ice (CO₂) |
| 0.01°C | 273.16 K | Triple point of water (ITS-90 definition) |
| 0°C | 273.15 K | Freezing point of water |
| 20°C | 293.15 K | Standard room temperature |
| 25°C | 298.15 K | Standard conditions (STP) for chemistry |
| 37°C | 310.15 K | Normal human body temperature |
| 100°C | 373.15 K | Boiling point of water (at 1 atm) |
| 232°C | 505.15 K | Melting point of tin |
| 327°C | 600.15 K | Melting point of lead |
| 660°C | 933.15 K | Melting point of aluminium |
| 1064°C | 1337.15 K | Melting point of gold |
| 1538°C | 1811.15 K | Melting point of iron |
Understanding Absolute Zero
Absolute zero (0 K = −273.15°C = −459.67°F) is the theoretical lower bound of temperature — the point at which all classical thermal motion of particles would cease. It is defined precisely by the laws of thermodynamics and cannot be reached in practice, only approached asymptotically.
| Temperature | Kelvin | °C | Context |
|---|---|---|---|
| Absolute zero | 0 K | −273.15°C | Theoretical minimum; unreachable |
| Coldest lab temp (approx.) | ~0.000000001 K | ≈ −273.15°C | Bose-Einstein condensate experiments |
| Liquid helium | 4.2 K | −268.95°C | Used to cool superconducting magnets (MRI) |
| Cosmic Microwave Background | 2.725 K | −270.425°C | Residual heat from the Big Bang |
| Outer space (average) | ~2.7 K | ~−270.45°C | Temperature far from any star |
Scientific & Physical Contexts
Kelvin is the required unit for thermodynamic calculations. Here are the fields where Kelvin appears most often and the typical temperature ranges involved:
| Field / Application | Typical Range (K) | Typical Range (°C) |
|---|---|---|
| Cryogenics / superconductors | 0–20 K | −273 to −253°C |
| Liquid nitrogen applications | 63–77 K | −210 to −196°C |
| Deep freeze / polar climate | 200–250 K | −73 to −23°C |
| Earth's climate range | 184–330 K | −89 to +57°C |
| Human body temperature | 309–311 K | 36–38°C |
| Combustion / flame | 1000–2500 K | 727–2227°C |
| Surface of the Sun | ~5778 K | ~5505°C |
| Lightning channel | ~30,000 K | ~29,727°C |
| Core of the Sun | ~15,000,000 K | ~15,000,000°C |
Full Conversion Table (−273°C to 2000°C)
| °C | K | °C | K | °C | K |
|---|---|---|---|---|---|
| −273.15 | 0.00 | 0 | 273.15 | 200 | 473.15 |
| −270 | 3.15 | 5 | 278.15 | 250 | 523.15 |
| −250 | 23.15 | 10 | 283.15 | 300 | 573.15 |
| −200 | 73.15 | 15 | 288.15 | 400 | 673.15 |
| −195.8 | 77.35 | 20 | 293.15 | 500 | 773.15 |
| −183 | 90.15 | 25 | 298.15 | 600 | 873.15 |
| −150 | 123.15 | 30 | 303.15 | 700 | 973.15 |
| −100 | 173.15 | 37 | 310.15 | 800 | 1073.15 |
| −78.5 | 194.65 | 40 | 313.15 | 900 | 1173.15 |
| −50 | 223.15 | 50 | 323.15 | 1000 | 1273.15 |
| −40 | 233.15 | 60 | 333.15 | 1200 | 1473.15 |
| −30 | 243.15 | 70 | 343.15 | 1500 | 1773.15 |
| −20 | 253.15 | 80 | 353.15 | 1800 | 2073.15 |
| −10 | 263.15 | 100 | 373.15 | 2000 | 2273.15 |
| −5 | 268.15 | 150 | 423.15 | — | — |
Frequently Asked Questions
What is 0°C in Kelvin?
0°C equals 273.15 K. This is the freezing point of water at standard atmospheric pressure. Formula: 0 + 273.15 = 273.15 K.
What is 25°C in Kelvin?
25°C equals 298.15 K. This is the standard temperature used in chemistry (often called "standard conditions" or STP in many textbooks). It's also close to a comfortable warm room temperature. Formula: 25 + 273.15 = 298.15 K.
What is 100°C in Kelvin?
100°C equals 373.15 K. This is the boiling point of water at standard sea-level pressure (1 atm / 101.325 kPa). Formula: 100 + 273.15 = 373.15 K.
Why is the Kelvin scale used in science instead of Celsius?
Kelvin is the thermodynamic temperature scale — its zero point (0 K) is absolute zero, the lowest possible temperature. Many fundamental physics equations (ideal gas law, blackbody radiation, thermodynamic efficiency) require an absolute temperature scale. If you used Celsius, where 0°C is an arbitrary point (water's freezing point), these equations produce incorrect results. Kelvin has the same degree size as Celsius, so converting is trivial — it's just the zero that matters.
Can temperature go below 0 Kelvin?
By the classical definition, no — 0 K is absolute zero, the theoretical minimum. However, certain quantum systems can achieve what are called "negative absolute temperatures", which are actually hotter than any positive temperature, not colder. These are exotic quantum states, not colder-than-absolute-zero temperatures in any everyday sense.
Do you write "degrees Kelvin" or just "Kelvin"?
The correct usage is just "Kelvin" (symbol: K), not "degrees Kelvin" or "°K". The BIPM (International Bureau of Weights and Measures) specifies that the kelvin is written without the degree symbol. This distinguishes it from Celsius (°C) and Fahrenheit (°F), which both use the degree symbol because they are interval scales, not absolute ones.
Sources & References
- BIPM – SI Units – defines the kelvin as an SI base unit
- NIST – ITS-90 Temperature Scale – International Temperature Scale of 1990
- NIST – Triple Point of Water – 273.16 K definition
Related Temperature Converters
Author
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