Kelvin to Celsius converter, subtract 273.15, no degree sign on the K.

To convert kelvin to Celsius, subtract 273.15. So 273.15 K is 0 °C, 300 K is 26.85 °C and 373.15 K is 100 °C. If you have heard "degrees kelvin", the word degrees is not used with this unit: it is just kelvin, written K.

How to use the converter

1. Type the number in the Kelvins (K) box. Leave off any degree sign.
2. The big result shows Degrees Celsius (°C). A card under it shows the same temperature in Fahrenheit.
3. Type Celsius in the second box to get kelvin, or press S to swap the two boxes.
4. Set Decimals to 2 or more to keep the .15. Click a row in Common values to load it.
5. Use Copy result or Print chart for a sheet that runs from 0 K upward.

The exact rule

NIST Handbook 44 (2026), Appendix C gives °C = K − 273.15 under "Conversion Equations for Units of Temperature (Exact)". NIST, SI units: temperature says zero degrees Celsius is 273.15 K and that one Celsius degree is an interval of 1 K. Pages checked 19 Oct 2026. The numbers are exact, so the result is exact up to the decimals you choose.

Why it is not degrees kelvin

BIPM, history of the kelvin says the 13th General Conference on Weights and Measures adopted the name kelvin, with symbol K, instead of "degree kelvin" with symbol °K. NIST, Kelvin: Introduction says the kelvin unit is not expressed in degrees like Celsius or Fahrenheit are. So write 300 K. Do not write 300 °K, and do not say 300 degrees kelvin. The degree sign stays with Celsius and Fahrenheit.

A ladder you can learn

Because the two scales have the same step, every 10 K is 10 °C. Once you know one point, the rest follow.

Worked examples

• 300 K. 300 − 273.15 = 26.85 °C.
• 310 K. 310 − 273.15 = 36.85 °C.
• 77 K. 77 − 273.15 = -196.15 °C. The answer is negative, and that is fine for Celsius.
• 0 K. 0 − 273.15 = -273.15 °C. NIST says 0 K is commonly called absolute zero.
• 273.16 K. 0.01 °C. NIST gives 273.16 K for the triple point of water.
• 5000 K. 4,726.85 °C, so at high values the two scales differ only by 273.15.

Warnings the tool gives

If you type a negative number in the kelvin box, the tool shows "Below 0 K". The scale starts at 0 K, which is -273.15 °C, so a negative kelvin is almost always a typing slip, such as a minus sign left over from a Celsius value. Check the number and the unit you meant.

Choosing the decimals

The Decimals setting rounds once, at the end, half away from zero. Take 300.5 K. With 2 decimals it is 27.35 °C, with 1 decimal it is 27.4 °C and with 0 decimals it is 27 °C. Use 2 decimals when you want to see the .15 at work, and 0 for a figure you will say out loud. Type the number only. A letter K or a degree sign in the box makes it unreadable, and the tool says so.

One temperature on three scales

Fahrenheit follows from the exact equations in the NIST Handbook table. The tool does the whole chain from kelvin, so there is no rounding in the middle.

Doing it without the tool

Take off 273, then take off 0.15 more. For 350 K: 350 − 273 = 77, and 77 − 0.15 = 76.85 °C. With decimals, 293.5 K is 20.35 °C. If you only need a rough figure, stop at 77. The tool keeps the .15 so a long chain of sums does not drift.

Mistakes that are specific to kelvin to Celsius

The first is subtracting 273. That is 0.15 off every time: 300 K gives 27 °C with the short constant and 26.85 °C with the exact one. The second is adding when you should subtract. Kelvin to Celsius always gives a smaller number. The third is using the offset on a difference. A change of one kelvin is the same amount of change as one degree Celsius, so a rise of 10 K is a rise of 10 °C, and you do not subtract anything. The fourth is the degree sign, covered above.

Who uses kelvin to Celsius

Students who got a kelvin answer and need a temperature they can picture. Anyone reading a data sheet or a science text that gives K. To go the other way open Celsius to Kelvin. For everyday scales see Celsius to Fahrenheit.