The functional Monte Carlo method devised by one of the authors for the efficiency and accuracy can be used to calculate universal scaling functions. In order to demonstrate the technique we take Istate Potts model for which many of the exact critical properties are known. Various thermodynamic functions of Potts model on square lattice of sizes ranging from 6 X 6 to 33 X 33 are calculated and the two scale factor universality (or hyperuniversality) theory put forward by Privman and Fisher is tested and verified. We also estimate the higher order derivatives of universal function using hyperuniversality hypothesis.