This publication presents novel equations which enable the direct analytical calculation the interaction torque between perpendicularly magnetized cuboidal permanent magnets in free space. These expressions complement the expressions for the interaction force and stiffness which are already available in literature and are computationally inexpensive due to their analytical nature. They are e.g. suitable in the design and analysis of ironless structures such as certain types of magnetic bearings or for obtaining the peeling torque on the magnets in devices such as voice coil actuators or electron beam focusing devices.