The magnetic vector potential for points throughout the magnetosphere has been obtained by integrating over a model magnetotail current system. Parameterized functions of x, y, z have then been fit to the potential at these points. The curl of the resultant vector potential function matches the computed magnetic field closely. The final expression for the field presented in this work is a good representation of the field from an arbitrarily thick (or thin) current sheet which diminishes antisolarward from the earth and returns on the surface of the magnetosphere.