Aisha K.
Mar 12, 2026
Clean layout and the results update instantly. Exactly what I needed for a quick planning check.
Unit Converters
Celsius to Kelvin Converter (°C to K)
Celsius
Going the other way? Open the reverse converter
°C → K
298.15 K
0 °C → 273.15 K. −273.15 °C → 0 K (absolute zero). 100 °C → 373.15 K.
- You typed
- 25 °C
- How it’s calculated
- K = °C + 273.15. The size of a kelvin equals a Celsius degree.
Celsius to Kelvin conversion table
Common °C values in K. Same factor as the converter above: K = °C + 273.15. The size of a kelvin equals a Celsius degree.
| Celsius | Kelvin |
|---|---|
| -10 °C | 263.15 K |
| 0 °C | 273.15 K |
| 0.25 °C | 273.4 K |
| 0.5 °C | 273.65 K |
| 1 °C | 274.15 K |
| 2 °C | 275.15 K |
| 5 °C | 278.15 K |
| 10 °C | 283.15 K |
| 20 °C | 293.15 K |
| 25 °C | 298.15 K |
| 32 °C | 305.15 K |
| 37 °C | 310.15 K |
Plain-English guide
Terms & how it works
Confused by a field? Read the short definitions here while you use the tool.
Celsius
The “Celsius” value used in this tool’s formula. Adjust it to see results update live.
K = °C + 273.15. The size of a kelvin equals a Celsius degree.
Labs and gas laws want kelvin because zero means zero motion, not “really cold in Celsius.” Add 273.15. You never write a degree sign on K. 25 °C room temp is 298.15 K.
How this calculator works
Labs and gas laws want kelvin because zero means zero motion, not “really cold in Celsius.” Add 273.15. You never write a degree sign on K. 25 °C room temp is 298.15 K. K = °C + 273.15. The size of a kelvin equals a Celsius degree. Scenario: 0 °C → 273.15 K. −273.15 °C → 0 K (absolute zero). 100 °C → 373.15 K.
K = °C + 273.15. The size of a kelvin equals a Celsius degree.
Scenario: 0 °C → 273.15 K. −273.15 °C → 0 K (absolute zero). 100 °C → 373.15 K.
When to use this Celsius to Kelvin
Common use cases
- Labs and gas laws want kelvin because zero means zero motion, not “really cold in Celsius.” Add 273.15. You never write a degree sign on K. 25 °C room temp is 298.15 K.
- Sanity-check with this scenario: 0 °C → 273.15 K. −273.15 °C → 0 K (absolute zero). 100 °C → 373.15 K.
- The relationship is: K = °C + 273.15. The size of a kelvin equals a Celsius degree.
Localized examples
- Unit Converters: the example on this page uses the same formula as the widget.
What you get
- Fields: Celsius
- K = °C + 273.15. The size of a kelvin equals a Celsius degree.
- Scenario on the page: 0 °C → 273.15 K. −273.15 °C → 0 K (absolute zero). 100 °C → 373.15 K.
How to Convert Celsius to Kelvin
- 1Enter Celsius. Use the values you have, not a catalog average, unless that is all you know.
- 2K = °C + 273.15. The size of a kelvin equals a Celsius degree.
- 3Scenario: 0 °C → 273.15 K. −273.15 °C → 0 K (absolute zero). 100 °C → 373.15 K.
- 4Check which dictionary the other person is using — US or UK, decimal or 1,024 — then trust the number.
Governing formula
K = °C + 273.15. The size of a kelvin equals a Celsius degree.
0 °C → 273.15 K. −273.15 °C → 0 K (absolute zero). 100 °C → 373.15 K.
0 °C → 273.15 K. −273.15 °C → 0 K (absolute zero). 100 °C → 373.15 K.
Variable definitions
- value
Celsius
The “Celsius” field. Default 25; typical range -273.15–5000.
- The conversion (K = °C + 273.15. The size of a kelvin equals a Celsius degree.) does not pick US vs UK gallons, SI vs binary megabytes, or Mach at altitude for you. Read the footnote on the page.
- Nothing here is uploaded for the calculation itself.
Frequently Asked Questions
Ice point is 273.15 K. Dropping the .15 is a lab error.
Related calculators
Unit Converters
- Celsius to RankineWhen a US customaries thermodynamics problem wants an absolute temperature but you measured Celsius: convert to kelvin, then × 9/5. 20 °C is 527.67 °R. Absolute zero is 0 °R on both sides of the ocean.
- Kelvin to CelsiusDatasheets list 298 K and you wanted “was that a warm lab?” Subtract 273.15. 298.15 K is 25 °C. Liquid nitrogen’s 77 K is −196 °C.
- Celsius Heat Units to JoulesA Celsius heat unit is the heat to raise 1 pound of water by 1 °C — about 1,899 J. Old HVAC and process papers use CHU. If you expected BTU, you are on the Fahrenheit twin (1 lb × 1 °F). Do not mix them in a load calc.
- Celsius to FahrenheitWeather apps, ovens, and fever debates. Multiply °C by 9/5 and add 32. Room temperature 20 °C is 68 °F. Body temperature 37 °C is 98.6 °F. The “times two plus 30” trick is only for sidewalks.
- Fahrenheit to CelsiusUS thermostats still speak Fahrenheit. Science and most of the planet speak Celsius. Subtract 32, then multiply by 5/9. 72 °F indoors is 22.2 °C, not “22 unless you like arguing about hoodies.”
- Fahrenheit to KelvinWhen a US weather number has to enter an ideal-gas problem: convert °F to °C in your head, then add 273.15 — or let this page do both. 68 °F is 293.15 K.
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4.8
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4 reviews
Daniel R.
Feb 28, 2026
Very usable on mobile. Would love a save/export option later, but the math feels solid.
Priya S.
Feb 3, 2026
The FAQ section answered my questions before I even had to search. Smooth dark mode too.
Marcus L.
Jan 19, 2026
Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.
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