1. A method for grading a food item comprising: singulating a supply of individual food items; imaging each of the food items to produce an image of each of the food items; computing an estimated weight of each of the food items using an image-to-weight function; weighing a sample of the food items to produce an actual weight of the weighed food items in the sample; comparing the estimated weights to the actual weights; adjusting the image-to-weight function based on the comparison of estimated weights to actual weights; grading the food item into a plurality of grades.