Crude Protein Calculator
Apply standard nitrogen-to-protein factors to quickly estimate crude protein content on as-is and dry bases.
Common factors: 6.38 for dairy, 5.7 for wheat, 6.25 general.
Enter for dry basis protein calculation.
Crude protein mass
0.78 g
Crude protein percent (as-is)
15.63 %
How to Use This Calculator
Analyze nitrogen content
Perform Kjeldahl or combustion nitrogen analysis and report the nitrogen percent on a mass basis.
Select the conversion factor
Choose the factor appropriate for the feed or food matrix (6.25 general, 6.38 dairy, 5.7 cereals, etc.).
Enter sample mass and optional moisture
Provide the mass analyzed and moisture fraction if you want dry basis output.
Review crude protein results
The tool displays protein mass and percent for both as-is and dry basis conditions.
Formula
Protein (g) = Sample mass × Nitrogen% / 100 × Conversion factor
Dry basis percent = Protein (g) / [Sample mass × (1 - Moisture%/100)] × 100.
Example
For a 5 g sample with 2.5 percent nitrogen and factor 6.25, crude protein equals 0.781 g, or 15.6 percent of the sample.
Full Description
Crude protein estimates assume a constant nitrogen to protein ratio. This approximation is widely used in food and feed labeling even though amino acid profiles vary.
Adjusting the conversion factor improves accuracy for specific materials, while dry basis reporting removes the effect of moisture content differences.
Frequently Asked Questions
Which conversion factor should I use?
6.25 is a general default. Dairy products often use 6.38 and wheat flour uses 5.7. Consult industry guidance for your material.
Does crude protein equal true protein?
No. Non-protein nitrogen inflates crude protein. Amino acid or true protein assays provide more detail.
Why is moisture optional?
Moisture corrections are needed when comparing protein on a dry basis. If you only need as-is values, leave moisture blank.
Can I enter nitrogen as mg/g?
Convert mg/g to percent by dividing by 10 before entering the value.
How accurate is the calculation?
Accuracy depends on nitrogen analysis quality and whether the chosen factor matches the sample composition.