Celsius to Kelvin formula
K = °C + 273.15 Example: 25°C + 273.15 = 298.15K About the Celsius scale
The Celsius scale is an intuitive, water-centric temperature system used globally for everyday weather, commerce, and cooking. Developed by Anders Celsius in 1742, it uses the freezing point of water at sea level as its 0°C baseline and the boiling point of water as 100°C. Because it relies heavily on these standard environmental thresholds, it is highly practical for global public use.
About the Kelvin scale
The Kelvin scale is the primary unit of temperature measurement in the physical sciences. Introduced by William Thomson (Lord Kelvin) in 1848, it transitions away from relative environmental benchmarks like freezing water. Instead, it anchors its absolute zero baseline (0K) at the thermodynamic point where all molecular motion completely stops.
Reference table
| Celsius | Kelvin |
|---|---|
| −273.15°C | 0K (absolute zero) |
| 0°C | 273.15K (freezing) |
| 20°C | 293.15K (room temperature) |
| 37°C | 310.15K (body temperature) |
| 100°C | 373.15K (boiling) |
Frequently asked questions
Why is Celsius to Kelvin just addition?
The Kelvin and Celsius scales use identically sized degrees — the only difference is where zero sits. Celsius starts at water's freezing point; Kelvin starts at absolute zero, which is 273.15 degrees colder. So converting is always just adding or subtracting that fixed offset.
What is absolute zero in Celsius?
Absolute zero is −273.15°C, equal to 0 Kelvin. This calculator will not accept a colder Celsius value, since none is physically possible.
Do Celsius and Kelvin ever show the same number?
No — they are always exactly 273.15 apart. Unlike Celsius and Fahrenheit, which cross at −40, Celsius and Kelvin never meet at the same number for any real temperature.
Need the reverse direction? See Kelvin to Celsius.