A follower element flowmeter which includes a hollow enclosed toroidal path around which a follower element travels in response to a flowing fluid. A pair of sensors are located adjacent to the fluid inlet and outlet to sense the passage of the follower element. The transit times of the follower element from inlet to outlet and from outlet to inlet is determined. The internal torus is described by juxtaposed housing halves one of which contains the fluid inlet and one, the fluid outlet. The halves are constructed so as to be relatively rotatable such that the distance between the inlet and outlet may be varied to adjust the calibration of the flowmeter.