We detail techniques to optimise high-level classical simulations of Shor’s quantum factoring algorithm. Chief among these is to examine the entangling properties of the circuit and to effectively map it across the one-dimensional structure of a matrix product state. Compared to previous approaches whose space requirements depend on r, the solution to the underlying order-finding problem of Shor’s algorithm, our approach depends on its factors. We performed a matrix product state simulation of a 60-qubit instance of Shor’s algorithm that would otherwise be infeasible to complete without an optimised entanglement mapping.