25 °C to K
- Degrees Celsius (°C)
- 25 °C
- Kelvins
- 298.15 K
Checked against: Exact-fraction computation from the legal unit definitions
Degrees Celsius to kelvins converter
Convert degrees Celsius to kelvins (Celsius to Kelvin) with the exact formula, a conversion chart and worked steps.
By AdminDrafted with AI writing toolsUpdated Checked examples: 3
Kelvins
K
Kelvins: 298.15 K
- Conversion
- 25 °C = 298.15 K
25 °C is about 298.15 K.
Degrees Celsius to kelvins
Celsius to Kelvin chart
| Degrees Celsius | Kelvins |
|---|---|
| -273.15 | 0 |
| -100 | 173.15 |
| -40 | 233.15 |
| 0 | 273.15 |
| 20 | 293.15 |
| 25 | 298.15 |
| 37 | 310.15 |
| 100 | 373.15 |
| 1000 | 1,273.15 |
How it's calculated S
Apply the formula
About the degrees Celsius to kelvins converter
A Celsius reading may describe weather, a room or an oven setting. Temperature scales use different zero points, so a ratio alone is insufficient. Converting a temperature reading is also different from converting a temperature difference, where the offset cancels.
degree Celsius → kelvin uses a formula because the temperature scales start at different zero points. For example, 25 °C is about 298.15 K.
The Celsius and kelvin scales have the same step size; a Fahrenheit degree is 5/9 of a Celsius degree. Absolute zero is 0 K, −273.15 °C or −459.67 °F, and inputs below it are rejected.
How to convert Celsius to Kelvin
Add 273.15 to the Celsius reading: K = °C + 273.15. So 25 °C is 298.15 K, 0 °C is 273.15 K and 100 °C is 373.15 K. Convert this way before putting a temperature into a gas law or any other formula that needs absolute temperature.
Why you add 273.15
Kelvins and Celsius degrees are the same size, so converting only moves the zero. The kelvin scale counts up from absolute zero, which is −273.15 °C.
The 273.15 is a defined value, not a measured one, so the conversion adds no error of its own (NIST).
Celsius to Kelvin chart
| Degrees Celsius | Kelvins |
|---|---|
| -273.15 | 0 |
| -40 | 233.15 |
| 0 | 273.15 |
| 20 | 293.15 |
| 25 | 298.15 |
| 100 | 373.15 |
The kelvin scale has no negative values: −273.15 °C is 0 K, absolute zero, and nothing can be colder. Negative Celsius readings just give kelvin values below 273.15.
Worked examples
- Body temperature: 37 °C + 273.15 = 310.15 K.
- Dry ice: at normal air pressure it turns to gas at about −78.5 °C, and −78.5 + 273.15 = 194.65 K.
- Chemistry tables: thermodynamic data listed at 298.15 K are for 25 °C.
Gas laws need kelvins
At constant pressure, a gas's volume is proportional to its kelvin temperature, not its Celsius reading. Warming air from 20 °C to 40 °C does not double its volume: 313.15 K ÷ 293.15 K = 1.068, an increase of about 6.8%.
The ideal gas law calculator applies the same rule to pressure, volume and amount of gas.
A change of 1 °C is a change of 1 K
Differences need no offset. Warming from 20 °C to 25 °C is a rise of 5 °C, and also of 5 K. Adding 273.15 to that rise would give 278.15 K, which is a temperature reading, not a difference.
Common mistakes
- Rounding to 273. Every result comes out 0.15 K low: 37 °C becomes 310 K instead of 310.15 K.
- Writing °K. The unit is the kelvin, written K with no degree sign: 298.15 K.
- Getting a negative kelvin value. That signals an input below −273.15 °C or a number that was never in Celsius, so check the source unit.
Related temperature conversions
Use Kelvin to Celsius for the reverse step, Celsius to Fahrenheit for the US scale, and the temperature converter for Rankine and Réaumur.
Worked examples
0 °C to K
- Degrees Celsius (°C)
- 0 °C
- Kelvins
- 273.15 K
Checked against: Exact-fraction computation from the legal unit definitions
100 °C to K
- Degrees Celsius (°C)
- 100 °C
- Kelvins
- 373.15 K
Checked against: Exact-fraction computation from the legal unit definitions
Questions
What is the formula to convert degree Celsius → kelvin?
Use K = °C + 273.15. For example, 25 °C = 298.15 K. The kelvin and the Celsius degree have the same size, so only the zero point differs.
About this calculator
Sources
Checked against references
This calculator includes 3 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.