Crude Protein Calculator (Kjeldahl Method)

Your details

Use Kjeldahl mode when you have titration volumes from the lab. Use the direct mode if you already know the nitrogen percentage.
Volume of titrant (usually HCl or H2SO4) consumed in the reagent blank. Corrects for background nitrogen in the reagents.
mL
Volume of titrant consumed when back-titrating (or forward-titrating) the sample digest.
mL
Molar concentration of the standard acid (or base) used in the titration.
mol/L
Normality-to-molarity correction for the titrant. Equals 1.0 for a monoprotic acid such as HCl; equals 2.0 for a diprotic acid such as H2SO4 when expressed as molarity.
Dry weight of the sample digested. Use the as-is weight if you want as-received protein; use the dry-weight for dry-matter protein.
g
Factor to correct for any dilution of the digest before titration. Leave at 1.0 if no dilution was performed.
Selects the Jones factor for converting nitrogen to protein. Different protein fractions contain different proportions of non-protein nitrogen, so the factor varies by food type.
Crude ProteinLow Protein
10.81%

Crude protein content of the sample on an as-submitted basis

Nitrogen Content1.73%
Jones Factor Used6.25
Protein LevelLow (5-15%) - grains, vegetables
10.81 %
Very Low<5Low5-15Moderate15-25High25-50Very High50+

Crude protein: 10.81% - Low (5-15%)

  • The nitrogen content is 1.730%, and multiplying by the Jones factor 6.25 gives 10.81% crude protein.
  • This is a low-to-moderate protein level, typical of grains, starchy vegetables, and most processed cereal products.
  • The general factor of 6.25 assumes proteins are 16% nitrogen by mass. For more accurate results, select the food-specific Jones factor for your sample matrix.

Next stepCrude protein overstates true protein because it counts all nitrogen, including non-protein nitrogen (NPN) from urea, nucleic acids, and free amino acids. True digestible protein is typically 5-20% lower than the crude figure, depending on sample type.

 = Powered by OnlyCalculators