In this paper we present both finite element based and analytic model simulations of pentacene based organic thin film transistor. The finite element type simulation is done using Silvaco’s Atlas simulator and the analytic model simulation is performed using a Matlab code based on the standard transistor equations. Both the Atlas and Matlab simulations agree approximately with the published experimental result. The results of the simulations show a current ratio of 2.11×106 for Atlas and 1.8×107 for Matlab simulations. The threshold voltage extracted from the finite element type simulation is 1.1 V which is in good agreement with 1.2 V used for Matlab simulation. However, the contact resistance shows a quite significant variation between the two simulation mechanisms. The finite element type simulation gives a contact resistance of 10 kΩ whereas the Matlab simulation predicts a contact resistance 1.9 kΩ.