Celsius to Kelvin Converter

Change degrees Celsius to kelvin as you type, with the working shown, why kelvin has no degree sign, a chart of the temperatures people look up most and room temperature in kelvin. Type in the Kelvin box to go the other way.

Free to use
No sign-up
Numbers stay in your browser

Last updated: 8 November 2026

Convert Celsius to Kelvin

Celsius (°C)

Kelvin (K)

25 °C = 298.15 K

How 25 °C becomes 298.15 K

Step 1: + 273.1525 + 273.15 = 298.15 K
Same size degrees1 °C change = 1 K change
School shortcut25 + 273 = 298 K

Updates as you type. Type in either box. Need the other way? Kelvin to Celsius

Round to

Nothing can be colder than absolute zero: 0 K or −273.15 °C. Values below it are not accepted.

Quick Conversions

Celsius to Kelvin Formula

K = °C + 273.15

Add 273.15 to the Celsius number
Example: 25 °C + 273.15 = 298.15 K
Kelvin has no degree sign: write 298.15 K, not 298.15 °K
Absolute zero is 0 K, which is −273.15 °C

273 or 273.15?

School problems often add 273. The exact value is 273.15, so the answer is a little different.

Celsius	Exact (+ 273.15)	School (+ 273)
0 °C	273.15 K	273 K
20 °C	293.15 K	293 K
25 °C	298.15 K	298 K
37 °C	310.15 K	310 K
100 °C	373.15 K	373 K

Use 273.15 when you need the exact answer, and 273 only when your teacher or book says to.

Celsius to Kelvin Chart

From absolute zero to 1,000 °C. Click a row to convert it.

Celsius	Kelvin
	0 K
	73.15 K
	173.15 K
	223.15 K
	233.15 K
	253.15 K
	273.15 K
	283.15 K
	293.15 K
	298.15 K
	303.15 K
	310.15 K
	323.15 K
	373.15 K
	473.15 K
	773.15 K
	1,273.15 K

K = °C + 273.15. Use Print to print this page with the chart.

Most Searched Celsius Values

The Celsius temperatures people look up most. Click one to use it.

Celsius	Kelvin
	298.15 K
	293.15 K
	273.15 K
	310.15 K
	373.15 K

25 °C is the most searched value, then 20 °C and 0 °C.

Room Temperature in Kelvin

Room temperature is often quoted as about 20 to 22 °C. In kelvin that is:

Celsius	Kelvin
	293.15 K
	294.15 K
	295.15 K

There is no single official figure for room temperature, so use the value your book or instructions give.

Key Temperatures

The reference points, in kelvin, Celsius and Fahrenheit.

Point	K	°C	°F
Absolute zero	0	−273.15	−459.67
Triple point of water	273.16	0.01	32.02
Water freezes	273.15	0	32
Body temperature (typical)	310.15	37	98.6
Water boils (about, sea level)	373.15	100	212

Water boils at about 100 °C only at standard sea-level pressure.

Celsius vs Kelvin

The two scales use the same size of degree.

	Celsius	Kelvin
Symbol	°C	K (no degree sign)
Water freezes	0 °C	273.15 K
Steps freezing to boiling	100	100
Lowest possible	−273.15 °C	0 K
Negative values	Yes	None

A change of 1 °C is exactly a change of 1 K, so temperature differences are the same in both.

Other Temperature Scales

Temperature Converter, all four scales: Celsius, Fahrenheit, kelvin and Rankine, with all 12 formulas.
Celsius to Fahrenheit, the same page for °F.
Kelvin to Celsius, the same page the other way.
Fahrenheit to Kelvin, °F to kelvin.
Kelvin to Fahrenheit, kelvin to °F.

About Celsius to Kelvin Conversion

Type a Celsius temperature and the kelvin answer appears as you type, with the working. Use it for chemistry, physics, school and science. Your numbers never leave your browser. Use it for everyday sums, not as a laboratory instrument.

Use this free Celsius to Kelvin converter to change a temperature from degrees Celsius to kelvin. Type a number in the Celsius box and the kelvin answer appears as you type, with the working shown. You can also type in the Kelvin box to go the other way. Pick how many decimals to round to and copy a link to your conversion. Tables list a chart from absolute zero to 1,000 °C, the Celsius values people look up most, room temperature in kelvin, key temperatures such as absolute zero and the triple point of water, and the difference between 273 and 273.15. It is free and instant, and your numbers stay in your browser.

How to convert Celsius to Kelvin

Celsius and kelvin use the same size of degree, so you only add a fixed number. To change Celsius to kelvin, add 273.15.

K = °C + 273.15

For 25 °C: 25 + 273.15 = 298.15 K. For 0 °C, the freezing point of water: 0 + 273.15 = 273.15 K. For 100 °C, the boiling point at sea level: 100 + 273.15 = 373.15 K. To go back, subtract 273.15: °C = K − 273.15.

Why kelvin has no degree sign

Kelvin is the SI unit of temperature, so it is written with just the letter K: 298.15 K, not 298.15 °K. It used to be called "degree Kelvin", and many people still say degrees kelvin, but the unit is simply the kelvin. Celsius keeps the degree sign: 25 °C.

Should you add 273 or 273.15?

The exact value is 273.15. School problems often use 273 to keep the sums short, which makes the answer 0.15 K lower: 25 °C is 298.15 K exactly, and 298 K with the school shortcut. Use 273.15 when you need the exact answer and 273 only when your teacher or book says to.

Common conversions

0 °C is 273.15 K, 20 °C is 293.15 K, 25 °C is 298.15 K, 37 °C is 310.15 K and 100 °C is 373.15 K. The chart above lists more, from absolute zero to 1,000 °C, and the table of most searched values shows the ones people look up most.

Room temperature in kelvin

Room temperature is often quoted as about 20 to 22 °C, which is 293.15 to 295.15 K. There is no single official figure, so use the value that your book, lab or instructions give.

Absolute zero and the triple point of water

Absolute zero is the lowest temperature possible: 0 K, which is −273.15 °C. Kelvin starts there, so it has no negative values. The triple point of water, where ice, liquid water and vapour exist together, is 273.16 K, which is 0.01 °C.

Same size degrees

A change of 1 °C is exactly a change of 1 K. If a temperature rises by 10 °C it rises by 10 K, so temperature differences are the same in both scales. Only the starting point is different, and that is why you add 273.15.

Kelvin to Celsius

To go the other way, subtract 273.15: 300 K is 300 − 273.15 = 26.85 °C. You can do it here by typing in the Kelvin box, or use the Kelvin to Celsius converter, which has its own chart. For Celsius to Fahrenheit, use the Celsius to Fahrenheit converter, and for all four scales use the Temperature Converter.

Spelling

The correct spellings are Celsius and kelvin. Many people type "celcius", "calsius" or "kelivn", and this page is for them too.

View All Converters

Temperature Converter

Frequently Asked Questions

How do I convert Celsius to Kelvin?

Add 273.15 to the Celsius temperature. For example, 25 °C + 273.15 = 298.15 K, and 0 °C is 273.15 K.

What is the formula for Celsius to Kelvin?

K = °C + 273.15. To go the other way, °C = K − 273.15. A degree Celsius and a kelvin are the same size, so you only add or subtract the fixed number.

What is 25 °C in Kelvin?

298.15 K. The sum is 25 + 273.15 = 298.15.

What is 0 °C in Kelvin?

273.15 K, the freezing point of water.

What is 20 °C in Kelvin?

293.15 K. The sum is 20 + 273.15 = 293.15.

What is 37 °C in Kelvin?

310.15 K, the usual figure for normal body temperature. The sum is 37 + 273.15 = 310.15.

What is 100 °C in Kelvin?

373.15 K, the boiling point of water at standard sea-level pressure. The sum is 100 + 273.15 = 373.15.

What is room temperature in Kelvin?

Room temperature is often quoted as about 20 to 22 °C, which is 293.15 to 295.15 K. There is no single official figure, so use the value that your book, lab or instructions give.

Why does kelvin have no degree sign?

Kelvin is the SI unit of temperature, so it is written with just the letter K, such as 298.15 K. It used to be called degree Kelvin, and many people still say degrees kelvin, but the unit is simply the kelvin.

Do I add 273 or 273.15?

The exact value is 273.15. School problems often use 273, which makes the answer 0.15 K lower: 25 °C is 298.15 K exactly and 298 K with the shortcut. Use 273 only when your teacher or book says to.

Can kelvin be negative?

No. Kelvin starts at absolute zero, 0 K, the lowest temperature possible, so it has no negative values. Celsius can be negative, down to −273.15 °C.

What is absolute zero in Celsius and Kelvin?

0 K, which is −273.15 °C. Nothing can be colder, so the converter does not accept a lower value.

Is a change of 1 °C the same as a change of 1 K?

Yes. The two scales use the same size of degree, so a rise of 10 °C is a rise of 10 K. Only the starting points differ, which is why you add 273.15.

Is it Celsius or Celcius?

The correct spellings are Celsius and kelvin. Many people type celcius, calsius or kelivn, and this converter is for them too.

Can I convert Kelvin to Celsius here?

Yes. Type the number in the Kelvin box and the Celsius box shows the answer. For 300 K the sum is 300 − 273.15 = 26.85 °C.

Are my numbers saved or shared?

No. The conversion happens in your browser, and the numbers you type are not stored or sent to any server. A link you copy keeps the numbers after the # sign, which browsers never send to a server.