Abstract: A hay baler scale is provided for automatically weighing hay bales as they emerge from a hay baler. It includes a weighing platform attached to opening of a chute of the hay baler, and a controller with a display. When a hay bale emerges from the baler, it is rotated a quarter turn by the chute and ejected onto the weighing platform. The controller is programmed to wait until the bale has stopped bouncing by ignoring the first readings, take multiple samples of the bale's weight, and show the average on the display in about 0.75 second. The controller thus ensures that a reasonably accurate weighing is performed despite the weighing platform being attached to a moving and vibrating hay baler. In a second embodiment, the weighing platform is attached to the top of a chute, so that the bales slide onto the platform without turning.