Celsius to Kelvin

Kelvin appears mainly in scientific and engineering contexts, lab equipment readouts, and gas law calculations, where measuring from absolute zero rather than water's freezing point avoids negative numbers in physics formulas. The conversion is a fixed offset, add 273.15 to a Celsius reading, with no multiplication involved, since a kelvin and a Celsius degree are exactly the same size, which is itself a handy fact for checking a calculation by eye.

Astronomy is a second common setting: star and planetary temperatures are almost always reported in Kelvin, since there is no meaningful zero point on Celsius for objects that hot. The Sun's visible surface, for instance, is commonly cited at roughly 5,800 K, a figure that only makes sense once converted away from a Celsius-based lab reading taken here on Earth, and the same offset applies however extreme the temperature being converted.

Celsius and Kelvin are the same size degree, just shifted by a fixed amount, so this conversion is pure addition with no multiplication step at all.

Add 273.15 to the Celsius value:

Kelvin = Celsius + 273.15

Worked examples: 0°C + 273.15 = 273.15 K, 25°C + 273.15 = 298.15 K, and -273.15°C + 273.15 = 0 K, the point known as absolute zero, where this conversion bottoms out at exactly zero.

Because this is a simple offset, the Kelvin result always carries exactly the same decimal precision as the Celsius input; the only real precision choice is whether to round 273.15 to 273, which should be avoided for any scientific use, since it discards real information rather than rounding noise that can be safely dropped.

The most common mistake is using 273 instead of 273.15, which is close enough for a rough mental estimate but wrong for any precise calculation. A second mistake is trying to multiply, as with Fahrenheit, when Kelvin needs only the addition since its degree size matches Celsius exactly and there is no scaling factor to apply.