Comparative image analysis is utilized to determine the flow rate of fluids, such as, for example, drilling fluid, completion fluid or hydrocarbons. As fluid flows through a conduit or open trough, a flow rate measurement device illuminates the surface of the fluid. Images of common surface features are then acquired at some time interval. Thereafter, the displacement of the common surface features in the images is analyzed to determine the flow rate of the fluid. Thus, non-contact flow rate measurements of opaque and non-opaque fluids are obtained.