Dimensionsal methods provide three major advantages in verification , deviation , and changing the system of units . Any empirical formula that is derived based on this method has to be verified and propportionality constants found by experimental means . The presence or absence of certain factors - non dimensional constants or variables - cannot be identified by this method . So every dimensionally correct relation cannot be taken as perfectly correct.
If `alpha` kilogram , `beta` meter , and `gamma` second are the fundamental units , `1 cal` can be expressed in new units as `[ 1 cal = 4.2 J]`