Measurement apparatus having a cantilever and a fluid flow channel, the cantilever being positioned in the channel so that it projects in a direction parallel to the direction of fluid flow. In an associated method, the cantilever is positioned in a fluid flow channel such that the cantilever extends parallel with the direction of fluid flow in the channel. Fluid is caused to flow in the channel at a known velocity. The resonant frequency of the cantilever is measured at one or more velocities of fluid flow and calculating the spring constant of the cantilever using the measured resonant frequency or frequencies. If the spring constant of the cantilever is known, the measurement of resonant frequency of the cantilever is used to determine the velocity of the fluid flow.