Crude Protein Calculator
Use this crude protein calculator to convert nitrogen content into crude protein percentage, or estimate nitrogen percentage directly from a simplified Kjeldahl-style workflow.
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Run the calculator.
What This Crude Protein Calculator Helps You Do
This page covers the two practical starting points behind most crude-protein checks: you either already know the nitrogen percentage or you need to estimate it from a simplified Kjeldahl-style titration workflow. That keeps the page useful for both quick screening and lab-note verification.
The result always reports nitrogen percentage alongside crude protein so the conversion factor remains visible instead of being hidden inside the calculation.
How to Calculate Crude Protein Calculator
- Choose the starting data: Use nitrogen mode if you already know the nitrogen percentage, or use the simplified Kjeldahl mode if you need to derive it from titration inputs.
- Select the protein factor: Use the general factor 6.25 unless a food- or feed-specific Jones factor is available.
- Compute nitrogen percentage when needed: The Kjeldahl-style mode estimates nitrogen percentage from titrant volume, titrant molarity, sample mass, and optional correction factors.
- Interpret crude protein carefully: Crude protein is an estimate based on total nitrogen, so non-protein nitrogen sources can raise the reported value.
Crude Protein Calculator Formula
| Variable | Meaning | Unit |
|---|---|---|
| N (%) | Nitrogen percentage in the sample | % |
| factor | Protein conversion factor (Jones factor) | dimensionless |
| V | Titrant volume | mL |
| M | Titrant molarity | mol/L |
| sample mass | Mass of analyzed sample | g |
Use the worked examples below to check how the formula behaves with real values. If the result looks unexpected, verify the unit assumptions and the meaning of each variable before interpreting the answer.
Worked Examples
- Nitrogen: 2.10%
- Factor: 6.25
Result: Crude protein is 13.13%.
A moderate nitrogen level converts to a typical mid-range protein percentage for feed and food screening.
- Volume: 12.4 mL
- Molarity: 0.10 mol/L
- Sample mass: 0.80 g
- Acid factor: 1.00
- Dilution factor: 1.00
- Factor: 6.25
Result: Nitrogen is 2.17% and crude protein is 13.57%.
The nitrogen estimate is multiplied by the protein factor to obtain crude protein percentage.
- Nitrogen: 3.00%
- Factor: 6.38
Result: Crude protein is 19.14%.
Changing the Jones factor changes the protein estimate even when the nitrogen measurement stays the same.
- Nitrogen: 2.25%
- Factor: 5.70
Result: Crude protein is 12.83%.
Commodity-specific factors can be more appropriate than the default 6.25 in some food systems.
How to Interpret Your Results
| Range | Meaning | Action |
|---|---|---|
| Low nitrogen percentage | The sample contains relatively little total nitrogen. | Check whether the sample is dilute or whether a commodity-specific protein factor is needed. |
| Typical feed/food range | The result is plausible for screening and formulation work. | Compare against product specifications or label targets. |
| Very high crude protein | The sample may be protein-rich or may contain non-protein nitrogen. | Confirm with a more specific protein method if the distinction matters. |
Frequently Asked Questions
References
Last reviewed: March 2026