— For a differential-drive mobile robot equipped with an on-board range sensor, there are six parameters to calibrate: three for the odometry (radii and distance between the wheels), and three for the pose of the sensor with respect to the robot frame. This paper describes a method for calibrating all six parameters at the same time, with no need of external sensors or apparatuses, and no need to drive the robot along particular trajectories. We assume that the available data are: the measured axes velocities, and the range sensor measurements. The maximum-likelihood solution is found in closed form.