Work out protein from nitrogen (kjeldahl) instantly with clear inputs, formula shown and shareable results.
Kjeldahl determines total nitrogen, which is converted to crude protein by a factor reflecting the average nitrogen content of the protein: 6.25 generally, 6.38 for dairy, 5.7 for wheat and 5.71 for soy. Titrant volume times normality times 14.007 gives milligrams of nitrogen.
Nitrogen
N % = titre (mL) x normality x 14.007 x 100 / (sample mg)
Crude protein
Protein % = N % x conversion factor
Because it counts all nitrogen, including non-protein nitrogen from urea, nucleotides, ammonia and any adulterant such as melamine. It is not a direct measure of true protein.
The commodity-specific factor: 6.38 dairy, 5.70 wheat, 5.71 soy, 5.55 gelatin, 6.25 general. Regulatory labelling rules specify which factor applies in each jurisdiction.