how to calculate weight percent from ppm?
Converting from Parts Per Million (ppm) to Percent (%) In order to express the results as a percent, divide the nutrient content (which is expressed in ppm) by 10,000. For example, if the reported value for P2O5 is 2,690 ppm, the calculation to convert to percent would be: 2,690 ppm ÷ 10,000 = 0.269%.