This paper presents an analysis of magnetic field homogeneity of square and circular Helmholtz coils pairs. The analysis is based on the Bio-Savart law for which it performs a Taylor series approximation for the magnetic field at a point on the axis of symmetry, finding an approximate expression of the homogeneity with respect to the parameter radius / length. Finally, a computational model is performed in COMSOL and comparing the magnetic field distribution for both geometries.