Complete Protein Score Calculator

Enter your food's amino acid content (mg per gram of protein) to calculate its PDCAAS score, quality rating, and limiting amino acid based on the WHO 2007 reference pattern.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Enter Histidine Content (mg/g)
Input the amount of Histidine in milligrams per gram of protein for your food item. The WHO 2007 reference is 18 mg/g.
2
Enter Isoleucine Content (mg/g)
Provide the Isoleucine content in mg per gram of protein. The WHO 2007 reference is 31 mg/g.
3
Enter Leucine Content (mg/g)
Input the Leucine content in mg per gram of protein. The WHO 2007 reference is 63 mg/g.
4
Enter Lysine Content (mg/g)
Provide the Lysine content in mg per gram of protein. The WHO 2007 reference is 52 mg/g.
5
Enter Methionine + Cysteine Content (mg/g)
Input the combined Methionine and Cysteine content in mg per gram of protein. The WHO reference is 26 mg/g.
6
Enter Phenylalanine + Tyrosine Content (mg/g)
Provide the combined Phenylalanine and Tyrosine content in mg per gram of protein. The WHO reference is 46 mg/g.
7
Enter Threonine Content (mg/g)
Input the Threonine content in mg per gram of protein. The WHO 2007 reference is 27 mg/g.
8
Enter Tryptophan Content (mg/g)
Provide the Tryptophan content in mg per gram of protein. The WHO 2007 reference is 7.4 mg/g.
9
Enter Valine Content (mg/g)
Input the Valine content in mg per gram of protein. The WHO 2007 reference is 42 mg/g.
10
Review Your Results
The calculator will display the PDCAAS score, limiting amino acid, and overall protein quality rating.

Example Calculation

A nutritionist is evaluating the protein quality of a new plant-based protein blend using the WHO 2007 reference pattern.

Histidine (mg/g)

Isoleucine (mg/g)

Leucine (mg/g)

Lysine (mg/g)

Methionine + Cysteine (mg/g)

Phenylalanine + Tyrosine (mg/g)

Threonine (mg/g)

Tryptophan (mg/g)

Valine (mg/g)

Results

100.0%

Tips

Identify Your Limiting Amino Acid

The amino acid with the lowest score relative to the WHO reference is your 'limiting' amino acid. This is the bottleneck for protein synthesis from that food, even if other amino acids are abundant.

Combine Proteins Strategically

If a food has a low PDCAAS score due to a limiting amino acid, combine it with another protein source that is rich in that particular amino acid to create a complete protein meal. This is common in plant-based diets.

Understand the PDCAAS Cap

While a raw score might exceed 100%, the PDCAAS is capped at 100%. This indicates that, for human needs, the protein provides 100% of the essential amino acids required for optimal growth and maintenance, rendering additional amino acids beyond this point non-limiting.

The Complete Protein Score Calculator evaluates the quality of a food's protein by comparing its essential amino acid profile to the World Health Organization (WHO) 2007 reference pattern. This tool is fundamental for dietitians, athletes, and anyone managing specific dietary needs, providing a Protein Digestibility-Corrected Amino Acid Score (PDCAAS) and identifying the "limiting" amino acid. Understanding a protein's quality is crucial for optimizing nutrition in 2025, ensuring adequate intake of the building blocks our bodies require.

Why Protein Quality Matters for Nutrition

Protein quality is a critical factor in human nutrition because not all proteins are created equal. While all proteins are made of amino acids, only complete proteins provide all nine essential amino acids that our bodies cannot synthesize on their own. The biological value of a protein, and its ability to support growth, repair, and maintenance, directly depends on its amino acid profile and how well it matches human requirements. Consuming high-quality proteins ensures efficient protein synthesis, which is vital for muscle growth, immune function, and overall metabolic health, preventing deficiencies that can hinder physiological processes.

The PDCAAS Formula and Limiting Amino Acids

The Protein Digestibility-Corrected Amino Acid Score (PDCAAS) is a widely recognized method for assessing protein quality. It works by comparing the amount of each essential amino acid in a food protein to a reference amino acid profile (the WHO 2007 pattern) and then correcting for protein digestibility. The lowest ratio among all essential amino acids determines the chemical score, which is then multiplied by the protein's digestibility.

Amino Acid Score = (mg of AA in 1g test protein / mg of AA in 1g reference protein)
PDCAAS = (Lowest Amino Acid Score) × (Protein Digestibility)

The "limiting amino acid" is the essential amino acid that is found in the lowest proportion relative to the reference pattern. This amino acid effectively limits the body's ability to utilize all other amino acids for protein synthesis, much like the shortest stave in a barrel limits its overall capacity.

💡 After assessing a protein's quality, use our Recipe Macro Calculator to integrate it into your daily dietary goals and ensure you meet your essential amino acid intake.

Evaluating a Plant-Based Protein Blend

Imagine a nutritionist is analyzing a new plant-based protein blend to ensure it meets dietary needs. They have the following amino acid data for the blend:

Input Amino Acid Content:
- Histidine: 26 mg/g (WHO Ref: 18 mg/g)
- Isoleucine: 53 mg/g (WHO Ref: 31 mg/g)
- Leucine: 85 mg/g (WHO Ref: 63 mg/g)
- Lysine: 70 mg/g (WHO Ref: 52 mg/g)
- Methionine + Cysteine: 37 mg/g (WHO Ref: 26 mg/g)
- Phenylalanine + Tyrosine: 65 mg/g (WHO Ref: 46 mg/g)
- Threonine: 44 mg/g (WHO Ref: 27 mg/g)
- Tryptophan: 12 mg/g (WHO Ref: 7.4 mg/g)
- Valine: 60 mg/g (WHO Ref: 42 mg/g)
Calculate Individual Amino Acid Scores (relative to WHO reference):
- Histidine: 26/18 = 1.44
- Isoleucine: 53/31 = 1.71
- Leucine: 85/63 = 1.35
- Lysine: 70/52 = 1.35 (lowest score)
- Methionine + Cysteine: 37/26 = 1.42
- Phenylalanine + Tyrosine: 65/46 = 1.41
- Threonine: 44/27 = 1.63
- Tryptophan: 12/7.4 = 1.62
- Valine: 60/42 = 1.43
Identify Limiting Amino Acid: Lysine has the lowest score (1.35).
Determine PDCAAS: Assuming protein digestibility is 1 (for simplicity in this example, but it's often slightly less for plant proteins), the PDCAAS score is 1.35 * 100% = 135%. Since PDCAAS is capped at 100%, the final score is 100.0%.

The result indicates that this plant-based blend, despite Lysine being the relative limiting factor, still provides all essential amino acids in sufficient quantities to meet human needs, achieving the highest possible PDCAAS score.

💡 If you're adjusting recipes to meet specific protein quality goals, our Recipe Serving Size Scaler can help you accurately modify ingredient amounts while maintaining nutritional balance.

Optimizing Dietary Protein for Health and Performance

Optimizing dietary protein intake is essential for various health and performance goals, from building muscle mass to managing satiety. For active individuals and athletes, protein requirements are often higher, with recommendations ranging from 1.6 to 2.2 grams per kilogram of body weight daily to support muscle protein synthesis and recovery. For those on plant-based diets, understanding protein quality and the concept of complementary proteins (combining different plant sources like beans and rice to get all essential amino acids) is crucial. High-quality protein also plays a significant role in weight management by promoting fullness and preserving lean muscle mass during caloric restriction.

Typical PDCAAS Scores for Common Protein Sources

The PDCAAS system provides a clear hierarchy of protein quality, helping consumers and nutritionists make informed dietary choices. Many animal-derived proteins, as well as some isolated plant proteins, achieve the maximum possible PDCAAS score of 1.00 (or 100%). For instance, egg whites, whey protein, casein, and soy protein isolate all typically score 1.00. Beef generally scores around 0.92, while common legumes like black beans might range from 0.75 to 0.85, and whole wheat around 0.42. These benchmarks illustrate that while diverse diets can easily meet protein needs, individual food choices vary significantly in their complete amino acid profile, impacting their overall nutritional efficiency.

Frequently Asked Questions

What is a complete protein score?

A complete protein score, often represented by the Protein Digestibility-Corrected Amino Acid Score (PDCAAS), assesses a food's protein quality based on its essential amino acid content relative to human requirements and its digestibility. A score of 100% signifies a high-quality protein that provides all essential amino acids in adequate proportions after digestion.

Why are essential amino acids important?

Essential amino acids are critical because the human body cannot synthesize them on its own; they must be obtained through diet. There are nine essential amino acids, and they are the building blocks for all proteins in the body, vital for muscle repair, enzyme production, hormone synthesis, and overall physiological function. Deficiencies can impair growth and health.

How does the WHO 2007 reference pattern work?

The WHO 2007 reference pattern provides the ideal amino acid profile needed by humans, particularly for children aged 0-3 years, which is considered the most demanding for amino acid requirements. This pattern acts as a benchmark against which the amino acid content of a food protein is compared to determine its quality and identify any limiting amino acids.

What does 'limiting amino acid' mean?

A limiting amino acid is the essential amino acid present in the lowest quantity relative to the body's needs within a given protein source. It dictates how efficiently the body can utilize the other amino acids for protein synthesis. If one essential amino acid is scarce, the body cannot build new proteins effectively, even if other amino acids are plentiful.