How To Convert Celsius To Kelvin Calculator
Converting Celsius to kelvin looks almost too easy beside the Fahrenheit rule, and the reason is that only the zero point moves while the size of the degree stays exactly the same.
Temperature in kelvin
298.15
- Same reading in Fahrenheit
- 77
- Same reading in Rankine
- 536.67
- Round trip back to Celsius (check)
- 25
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
The formula this calculator uses
K = C + 273.15
- C
- Reading in degrees Celsius
- 273.15
- Offset between the Celsius zero and absolute zero
- K
- Same reading in kelvin, on an absolute scale
How to check the result by hand
- 1
Confirm you have a reading, not a difference
The offset applies only to an actual temperature. A rise of 25 C is a rise of 25 K with no 273.15 added, because subtracting two readings cancels the offset. Adding 273.15 to a change is the classic error on this page.
- 2
Add 273.15, and nothing else
25 + 273.15 = 298.15, so 25 C is 298.15 K. There is no factor of 9/5 and no multiplication of any kind; the only arithmetic is the single addition. If you find yourself multiplying, you have slipped back into the Fahrenheit conversion.
- 3
Check the sign and the size of the result
Any kelvin answer below 0 is impossible, so a negative result signals an error. A weather reading of 25 C should land near 298 K, and a freezing point of 0 C should land near 273 K. These rough targets catch a misplaced decimal immediately.
- 4
Use 273.15, not 273, when the number matters
The shortcut costs 0.15 K, which is 0.05 per cent of 298.15 K. That is invisible in a forecast but visible in the third significant figure of a gas-law calculation, so keep the full offset whenever the result feeds something else.
- 5
Round-trip to verify
Subtract 273.15 from the kelvin value and you should recover the Celsius reading exactly: 298.15 - 273.15 = 25. If the round trip misses, the offset was applied to the wrong quantity or with the wrong sign.
For worked examples, common mistakes and the limits of this formula, read the full How To Convert Celsius To Kelvin page.