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Protein From Nitrogen (Kjeldahl) Calculator

Work out protein from nitrogen (kjeldahl) instantly with clear inputs, formula shown and shareable results.

About Protein From Nitrogen (Kjeldahl) Calculator

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.

Formulas

Nitrogen

N % = titre (mL) x normality x 14.007 x 100 / (sample mg)

Crude protein

Protein % = N % x conversion factor

Worked example

With the default values below, Protein From Nitrogen (Kjeldahl) Calculator returns Crude Protein Content of 10.9430%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Titrant Volumeminimum 0 mL
12.5 mL
Acid Normalityminimum 0 N
0.1 N
Sample Weightminimum 0 g
1 g
Nitrogen To Protein Factorminimum 0.01
6.25

Results

Crude Protein Content
10.9430%
Nitrogen Content
1.75088%
Nitrogen Determined
17.5088
Energy From Protein Per 100 g
43.772

Step by step

  1. 1Values used
  2. 2Nitrogen
  3. 3Crude protein
  4. 4Crude Protein Content= 10.9430
  5. 5Nitrogen Content= 1.75088
  6. 6Nitrogen Determined= 17.5088
  7. 7Energy From Protein Per 100 g= 43.772

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is it called crude protein?

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.

Which factor should be used?

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.

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