k=c+273.15

0 Kelvin is commonly thought to be the lowest temperature possible!

It is equivalent to     -273.15 degrees Celcius 

http://www.sciencedaily.com/articles/a/absolute_zero.htm

http://en.wikipedia.org/wiki/Absolute_zero

k=c+273.15

K = °C + 273.15

Your answer will be in Kelvin.
Remember, the Kelvin temperature scale does not use the degree (°) symbol.

For example, if you want to know what 20°C is in Kelvin:

K = 20 + 273.15 = 293.15 K