A method of calibrating a yield sensor of a harvesting machine. The yield sensor generates a grain force signal as clean grain piles are thrown by the elevator flights against the sensor surface of the yield sensor. A grain height sensor is disposed to detect a height of the clean grain pile on each passing elevator flight. Each grain height signal is associated with a corresponding grain force signal by applying a time shift to account for a time delay between the time the grain height signal is generated and the time at which the impact signal is generated. The grain force signal is corrected by multiplying the grain force signal by a correction factor. The correction factor is the sum of the grain height signals divided by the sum of the grain force signals over a predetermined period.