I calculate cost per gram because it takes into account different serving sizes of protein powders. (purefoodcompany.com)
Kate — yes, under the National School Lunch Program, there are different serving sizes depending on the grade level. (thelunchtray.com)
K - 3 has different serving sizes than 4 - 12, etc. (I believe that in an elementary school that goes from K - 5 or 6, an average is used — but don't quote me on that.) (thelunchtray.com)