This contribution documents the methods used in the BioSaw code. The code is inteded to be a flexible tool for calculating magnetic fields due to coils in magnetic confinement fusion devices. It assumes the conductors are infinitesimally thin and can be described as either point sequences or circular coils. The code can calculate both the magnetic field as well as the vector potential due to the coils. The fields can be reduced very near the coils to avoid singular behaviour caused by the thin conductor approximation.