It has been observed that many students commit a mistake to add 273 in temperature difference while converting the temperature difference for a body in degree centigrade to kelvin. While is to be noted that if temeperature of a body is changed by t degree at centigrade scale then the temperature change at kelvin scale will be just t kelvin not t + 273.

Mathematically 

t = t2 - t1     degree centigrade

difference at kelvin scale will be t2 + 273 - (t1 + 273) = t2 - t1 

both have same numerical value.