Method: How proteinscore Calculates

The formula

For a meal made of several ingredients j and the nine essential amino acids i:

P_j

Amount of protein from ingredient j in g (amount × protein content)

a_ij

Content of amino acid i in the protein of ingredient j, in mg per g protein

d_ij

True ileal digestibility of this amino acid (the share absorbed in the small intestine)

r_i

Reference requirement for amino acid i in mg per g protein (table below)

Important: the amino acids are summed first and compared afterwards. Averaging the DIAAS values of the individual ingredients gives a wrong result, because the ingredients can complement each other.

Protein that actually counts

A DIAAS above 1 does not increase the amount: the body cannot build with more than 100 % of the protein eaten. The calculator also points it out when a meal contains less than about 2.5 g of leucine. Leucine is considered the start signal for muscle building.

Reference pattern

The requirement for essential amino acids per gram of protein for older children, adolescents and adults according to the FAO (2013):

Worked example: rice with lentils

200 g cooked rice (5.4 g protein) and 150 g cooked lentils (13.5 g protein), together 18.9 g protein.

The smallest number is 0.98, so DIAAS 98. Usable: 18.9 g × 0.98 = 18.5 g.

Rice alone comes to about 71 (lysine is missing), lentils alone to about 88 (methionine is missing). A protein-weighted average would be 83. Because the gaps fill each other, the combination reaches 98.

Rating scale

In the calculator, the levels are called "Top quality", "Good quality" and "Low quality".

What "usable" means

The calculator shows how many grams of your protein are usable. It is calculated as total protein times DIAAS, capped at 100 %. The FAO calls this quantity "utilizable protein": the amount of protein equivalent to a protein with an ideal composition.

An example: 250 g of pasta contains 14.5 g of protein with a DIAAS of 54. Mathematically, that equals 7.8 g of complete protein. That doesn't mean the rest disappears without a trace. But without a matching partner, the body cannot use the remaining amino acids to build body protein and uses them in other ways, for example as energy.

proteinscore gives a meal's Proteinscore as a percentage: the share of the protein that is fully usable. It equals the DIAAS, capped at 100 %. The DIAAS itself is shown uncapped in the calculator, so you can see how much headroom a food has to complement others. The calculator does not rate meals with less than 5 g of protein, because the number says little at that level.

Database

Every food in the database has one of three quality levels. The foods table shows it for each entry. All foods with a measured or derived value and their study are listed under Data & sources.

Dishes

proteinscore does not calculate dishes like lasagna or döner kebab as separate entries but through their ingredients. Each of the dishes is a standard recipe for one serving, for example lasagna sheets, ground beef, tomatoes, milk and cheese for lasagna. Oil, sugar and spices are left out because they provide no protein. In the calculator you can adjust servings and every ingredient. Because recipes vary a lot, the values are guidelines.

Limitations of the calculation

• Amino acid contents and digestibility are rounded literature values. Variety, growing conditions and preparation change them.
• Digestibility values per amino acid exist for relatively few foods. For the rest, we use a flat value per food group.
• The measurements come mostly from trials with pigs, whose digestion is similar to ours, and partly from rat studies and a lab study. For cooked egg there are measurements in humans.
• Processing changes the values. For bread we subtract 17 % of usable lysine for baking losses, for breadcrumbs 34 %. For potatoes and fries there is only transferred pig data, so these values are especially uncertain.
• The reference pattern applies to children from 3 years, adolescents and adults. For young children the values are lower.
• Whether proteins also complement each other across several meals has not been conclusively settled. The calculator rates each meal on its own.
• The calculator is not a substitute for dietary advice.

Sources

1. FAO (2013): Dietary protein quality evaluation in human nutrition. FAO Food and Nutrition Paper 92, Rome.
2. U.S. Department of Agriculture, Agricultural Research Service (2018): FoodData Central, SR Legacy. Protein contents and amino acid profiles for most of the foods.
3. Herreman, L. et al. (2020): Comprehensive overview of the quality of plant- and animal-sourced proteins based on the digestible indispensable amino acid score. Food Science & Nutrition 8(10), 5379–5391.
4. Fanelli, N. S., Stein, H. H. et al. (2021–2024): Additivity of values for digestible indispensable amino acid score in individual foods when included in mixed meals for humans. University of Illinois.
5. Rutherfurd, S. M., Fanning, A. C., Miller, B. J. & Moughan, P. J. (2015): Protein digestibility-corrected amino acid scores and digestible indispensable amino acid scores differentially describe protein quality in growing male rats. Journal of Nutrition 145(2), 372–379.
6. Mathai, J. K., Liu, Y. & Stein, H. H. (2017): Values for digestible indispensable amino acid scores (DIAAS) for some dairy and plant proteins may better describe protein quality than values calculated using the concept for protein digestibility-corrected amino acid scores (PDCAAS). British Journal of Nutrition 117, 490–499.
7. Bailey, H. M., Mathai, J. K., Berg, E. P. & Stein, H. H. (2020): Most meat products have digestible indispensable amino acid scores that are greater than 100, but processing may increase or reduce protein quality. British Journal of Nutrition 124, 14–22.
8. Bailey, H. M. & Stein, H. H. (2020): Raw and roasted pistachio nuts (Pistacia vera L.) are ‘good’ sources of protein based on their digestible indispensable amino acid score as determined in pigs. Journal of the Science of Food and Agriculture 100, 3878–3885.
9. Alotaibi, M., Muleya, M., Salter, A., Hoad, C. & Eldeghaidy, S. (2026): Comparison of the protein quality of chicken and plant-based chicken analogues using the INFOGEST in-vitro digestion system. Food Chemistry 520, 149734.
10. Kendler, S., Thornes, F. W., Jakobsen, A. N. et al. (2023): Nutritional profiling and contaminant levels of five underutilized fish species in Norway. Frontiers in Nutrition 10, 1118094.
11. Reynaud, Y., Buffière, C., Cohade, B., Vauris, M., Liebermann, K., Hafnaoui, N., Lopez, M., Souchon, I., Dupont, D. & Rémond, D. (2021): True ileal amino acid digestibility and digestible indispensable amino acid scores (DIAASs) of plant-based protein foods. Food Chemistry 338, 128020.
12. Stroebinger, N., Hodgkinson, S. M. & Moughan, P. J. (2024): Pig true ileal digestible amino acid contents of individual ingredients are additive in mixed meals and allow accurate predictions of digestible indispensable amino acid score values. Journal of Nutrition 154, 3323–3330.
13. Gilani, S., Tomé, D., Moughan, P. J. & Burlingame, B. (2012): Report of a sub-committee of the 2011 FAO Consultation on "Protein quality evaluation in human nutrition", with appendix: True ileal amino acid and protein digestibility for selected human foods (Moughan & Rutherfurd). FAO, Rome.
14. Moughan, P. J. & Lim, W. X. J. (2024): Digestible indispensable amino acid score (DIAAS): 10 years on. Frontiers in Nutrition 11.