In this work we propose a novel method to calibrate the projector. Calibration of the projector deals with the calculation of geometric parameters of the projector which are intrinsic and extrinsic parameters. An un-calibrated camera assists the process of finding the geometric parameters for projector. This method exploits the fact that a projector can be treated as inverse camera. The camera captures the scene and saves it as an image while the projector projects an image on the scene. Camera to projector transformation is used to make the projector able to see the calibration pattern. Then the projector is calibrated in a similar fashion like camera. Real data is used to evaluate the proposed method of projector calibration and good results are obtained.