A generalized equation is derived which describes the loss coefficient for any differential pressure type fluid meter. This loss coefficient is given in terms of dimensionless factors including: meter geometry, discharge coefficient, contraction coefficient, and diffuser efficiency. The equation applies equally well for venturis, nozzles, and orifices, installed in pipes or with plenum inlets. Another equation is derived which relates the previously published ASME loss parameter for fluid meters to this new generalized loss coefficient.