In this paper we have proposed an image-processing algorithm for auto evaluation of OMR answer sheets using the mobile application. Multiple-choice questions are widespread mechanism used by different schools and universities to evaluate student performance. They are common tests on standard basis. Big organizations use OMR forms coupled with OMR software and dedicated scanner for evaluatingOMR based multiplechoice questions. But small institutes and individual teachers cannot afford this costly setup and have to do time consuming manual grading. So we propose a mobile application that can be used by anyone at any time to evaluate answer sheets and save the valuable time spent grading manually. First we will discuss the OpenCV implementation of the image-processing algorithm and report on its challenges. Second we will give an overview of what was implemented on the android phone. Finally we will summarize the challenges and possibilities for future work.