Dimensions of grains are important factors in evaluating the physical quality of the grains. In this work, we show for the first time that the thickness, the width, and the length of rice grains can be simultaneously measured. Rather than imaging rice grains only above from a two-dimensional plane, our key idea is to insert a tilt reflective surface on the measuring plane such that the side view of the rice grains can be observed at the same time. Demonstration from our prototype shows a very promising result in determining the thickness, the width, and the length of the rice grain with maximum values of 2.20 mm, 3.65 mm, and 10.27 mm, respectively. It offers a very high average resolution of 22 μm and a measured response time of 205 ms. Additional key features include low cost, low components count, and ease of implementation.