A laundry treating appliance for treating a laundry load according to at least one cycle of operation including a rotatable drum at least partially defining a treating chamber in which a laundry load is received for treatment, a motor rotatably driving the drum in response to a motor control signal, and a controller outputting a motor control signal to rotate the drum according to a speed profile having at least a constant speed phase, where the drum is rotated at a constant speed, and an acceleration phase, where the drum is accelerated to the constant speed and a method of operating a laundry treating appliance to determine an inertia of the laundry load.