PDCAAS Calculator (Protein Digestibility Corrected Amino Acid Score)
Estimate protein quality for foods and blends using amino acid profile and digestibility.
Single protein: one food or isolate. Blend: mix of multiple protein sources (e.g., rice + pea).
Values in mg of amino acid per g of reference protein.
Typical values: 90–98% for animal proteins, 70–95% for plant proteins.
| Indispensable amino acid |
Content (mg / g protein) |
Reference (mg / g) |
Ratio (test / ref) |
|---|
Enter amino acid content per gram of protein (not per 100 g of food). If you only have values per 100 g of food, divide by grams of protein per 100 g.
Results
Enter data and click “Calculate PDCAAS” to see an interpretation of protein quality.
Formula
Step 1 – Amino acid score (AAS):
For each indispensable amino acid \(i\):
\(\text{ratio}_i = \dfrac{\text{mg of amino acid } i \text{ per g test protein}}{\text{mg of amino acid } i \text{ per g reference protein}}\)
The amino acid score is the minimum of all ratios:
\(\text{AAS} = \min(\text{ratio}_i)\)
Step 2 – Apply digestibility:
\(\text{PDCAAS}_\text{raw} = \text{AAS} \times \dfrac{\text{digestibility (\%)}}{100}\)
Step 3 – Truncate at 1.0: \(\text{PDCAAS} = \min(1.0, \text{PDCAAS}_\text{raw})\)
What is PDCAAS?
PDCAAS stands for Protein Digestibility Corrected Amino Acid Score. It is a widely used method to rate the quality of dietary protein on a scale from 0 to 1.0, based on:
- how well the protein’s essential amino acid profile matches human requirements, and
- how much of that protein is actually digested and absorbed (true digestibility).
A PDCAAS of 1.0 means the protein provides all indispensable amino acids in sufficient amounts after accounting for digestibility. This is the maximum score (values above 1.0 are truncated).
Typical PDCAAS values for common proteins
| Protein source | Approx. PDCAAS | Notes |
|---|---|---|
| Egg, milk, whey, casein | 1.0 | Complete amino acid profile, very high digestibility. |
| Soy protein isolate | ~1.0 | Plant protein with PDCAAS comparable to animal proteins. |
| Beef, poultry, fish | 0.9–1.0 | High-quality animal proteins. |
| Pea protein | ~0.7–0.9 | Often limited by methionine + cysteine. |
| Wheat protein (gluten) | ~0.4–0.5 | Low in lysine; digestibility varies with processing. |
| Rice protein | ~0.5–0.7 | Limited in lysine; often combined with legumes. |
| Mixed plant protein blends | 0.8–1.0 | Complementary amino acid profiles can reach PDCAAS 1.0. |
Values are approximate and depend on variety, processing, and measurement methods. For labeling or clinical use, rely on lab analyses and official reference data.
How this PDCAAS calculator works
This tool follows the standard PDCAAS methodology in three steps:
- Normalize amino acids per gram of protein (mg/g protein).
- Compare to a reference pattern (FAO/WHO/UNU 2007) for the chosen age group.
- Apply true protein digestibility and truncate the final score at 1.0.
For blends, the calculator first computes a weighted average amino acid profile based on the percentage of total protein from each source, then applies the same PDCAAS steps.
Reference amino acid patterns used
The reference values (mg amino acid per g reference protein) are based on FAO/WHO/UNU recommendations:
- 6–12 months: highest requirements per gram of protein.
- 1–2 years: slightly lower than infants.
- ≥3 years & adults: used for most adult applications and labeling.
Choosing a pattern with higher requirements (e.g., infants) will generally yield a lower PDCAAS for the same protein, because the benchmark is stricter.
Interpreting your PDCAAS result
- 0.9–1.0: very high-quality protein; fully adequate for the chosen reference pattern.
- 0.7–0.89: good quality; may be slightly limited in one amino acid.
- 0.4–0.69: moderate quality; useful in mixed diets or blends.
- <0.4: low quality as a sole protein source; usually needs complementation.
Remember that PDCAAS is one metric. Total protein intake, energy intake, overall diet quality, and individual health status are also important.
Limitations of PDCAAS
- Scores are truncated at 1.0, so proteins better than the reference pattern still show as 1.0.
- Uses overall fecal protein digestibility, not amino-acid–specific ileal digestibility (as in DIAAS), which may underestimate or overestimate some proteins.
- Does not account for anti-nutritional factors or processing effects beyond their impact on digestibility.
- Assumes the reference pattern is appropriate for the population being considered.
For research or regulatory work, consult the latest FAO/WHO reports and peer-reviewed literature on protein quality assessment.
Practical tips for using this calculator
- Use lab analyses or authoritative food composition tables for amino acid values whenever possible.
- If you only know amino acids per 100 g of food and grams of protein per 100 g, convert to mg/g protein by dividing amino acid (mg/100 g food) by protein (g/100 g food).
- For plant-based formulations, experiment with different blend ratios to see how PDCAAS changes and which amino acid becomes limiting.
- Use realistic digestibility values; if unknown, base them on similar foods reported in the literature.
Disclaimer
This calculator is for educational and formulation support only. It does not replace laboratory testing, regulatory guidance, or personalized advice from a qualified dietitian, nutritionist, or physician. For clinical nutrition, infant formulas, or product labeling, always rely on validated analytical data and applicable regulations.