The dispersion relation of magnetostatic surface waves propagating in a ferromagnetic film of finite dimensions is derived. Specifically, a consideration of the finite width of the sample is introduced to the previous treatments of magnetostatic surface‐wave propagation. The inclusion of a finite width produces a multiplicity of propagating modes, which can be excited individually or collectively, depending on experimental conditions. In addition, the finite width allows the excitation of magnetostatic volume waves, which exist over a narrow frequency range just below the range of magnetostatic surface waves. All aspects of the theoretical analysis are supported by measurements made on magnetostatic surface‐wave propagation at frequencies around 1 and 9 GHz in yttrium iron garnet samples of different widths.