To gain fundamental insight into granular flow behaviour, quantitative measurements of velocity and solid fraction are required. The aim of this study is to measure the solid fraction and velocity of 3D granular flows quantitively using a recently developed MRI method. Time-averaged spatial maps of the solid fraction and velocity are obtained for hoppers with wall angles of 30°, 60°, and 90°. From these maps, the mass flow rate of the material was calculated along the height of the hoppers. Excellent agreement was observed between the MRI and gravimetric mass flow rate measurements, confirming the quantitative nature of the measurements. The resulting solid fraction and velocity measurements provide insight into the dynamics of granular flow.