The long-range magnetic field is the most time-consuming part of micromagnetic simulations. Computational improvements can relieve problems related to this bottleneck. This work presents an effcient implementation of the Fast Multipole Method [FMM] for the magnetic scalar potential and stray field as used in micromagnetics. The novelty lies in extending FMM to linearly magnetized tetrahedral sources making it interesting also for other areas of computational physics. The near field is calculated directly, and the far field is approximated numerically using multipole expansion. This approach tackles important issues like the vectorial and continuous nature of the magnetic field. By using FMM the calculations scale linearly in time and memory and are distributed among many processors.