An instrument drive unit for use with a surgical robotic arm includes a body, a first gear, and a driven coupler. The body has a proximal end and a distal end configured to be coupled to a surgical instrument. The first gear is non-rotatably coupled to the proximal end of the body. The driven coupler is disposed at the proximal end of the body and laterally offset from the first gear. The driven coupler is operably coupled to the first gear such that rotation of the driven coupler rotates the first gear to effect rotation of the body about a longitudinal axis defined by the body.
