Protein Units Explained: Grams, Grams per Kilogram, Percent of Calories and How to Convert Them
How protein is counted in grams per day, grams per kilogram of body weight and percent of calories, how to convert between them, and why official figures are not interchangeable.
Content last updated . This page has not been medically reviewed.
The three units side by side
| Unit | What it measures | Where you meet it |
|---|---|---|
| Grams per day (g/day) | Total protein eaten in a day | Food labels, intake tables, tracking apps |
| Grams per kilogram per day (g/kg/day) | Protein scaled to body weight | Reference values such as an RDA or a Population Reference Intake |
| Percent of calories (% of energy, "E%") | The share of energy that comes from protein | Acceptable ranges for the whole diet |
Health Canada's table gives an adult reference value both ways: 0.80 g/kg/day and, for adult men and women aged 19 to 50, 56 g/day and 46 g/day. [2] The same table gives a range in percent of energy, which is a third unit again. [2]
Published reference values (each with population, body and year)
| Group | Value and unit | Source and year |
|---|---|---|
| Adults 19 to 50, men | RDA 0.80 g/kg/day; 56 g/day | Health Canada, Dietary Reference Intakes macronutrient table (2005 table) [2] |
| Adults 19 to 50, women | RDA 0.80 g/kg/day; 46 g/day | Health Canada (2005 table) [2] |
| Pregnancy, ages 19 to 50 | RDA 1.1 g/kg/day; 71 g/day (second half of pregnancy only) | Health Canada (2005 table) [2] |
| Lactation, ages 19 to 50 | RDA 1.3 g/kg/day; 71 g/day | Health Canada (2005 table) [2] |
| Adults 19 and over | Acceptable range 10% to 35% of energy | Health Canada (2005 table) [2] |
| Healthy adults, Europe | Population Reference Intake 0.83 g/kg/day | EFSA 2012, as reproduced by the European Commission's Knowledge4Policy page [3] |
| Adults, Nordic countries | 0.83 g/kg/day; recommended range 10 to 20 E% | Nordic Nutrition Recommendations 2023, as reproduced by Knowledge4Policy [3] |
| Packaged food labels, adults and children 4 and over, US | Daily Value of 50 g (a label reference, not a requirement) | US federal regulation 21 CFR 101.9 [4]; FDA [5] |
These numbers differ by country, year and purpose. None is the single "correct" figure. How agencies set them is explained in How Protein Requirements Are Set.
Worked examples with made-up numbers
Grams per kilogram to grams per day. Multiply the per-kilogram value by body weight. A made-up person of 60 kg and a made-up value of 0.80 g/kg/day gives 0.80 × 60 = 48 g/day. This shows the arithmetic only.Pounds to kilograms. The US National Institute of Standards and Technology lists 0.4535924 kilograms per pound. [6] So 150 lb × 0.4535924 is about 68 kg. A per-kilogram value times 0.4535924 gives the per-pound value: 0.80 g/kg is about 0.36 g/lb.
Grams to percent of calories. MedlinePlus states that one gram of protein supplies 4 calories, and gives the example of 100 g of protein on a 2,000 calorie diet as 400 calories, or 20% of calories. [1] Formula: grams × 4 ÷ total calories × 100. A made-up shake with 25 g of protein and 300 calories gives 25 × 4 = 100 calories, which is one third (33%) of that shake's calories.
Why one g/kg value can mean different percentages. The French agency ANSES, as reproduced on Knowledge4Policy, described intakes of 0.83 to 2.2 g/kg/day as 10 to 27% of energy intake for adults under 60. [3] The percentage depends on how many calories a person eats. The Nordic recommendations note that when energy intake is low, the protein percentage must rise to meet the same g/kg value. [3]
A powder label percentage. If a made-up 30 g scoop lists 24 g of protein, protein is 80% of the powder by weight (24 ÷ 30). That is a different "percent" from percent of calories and from percent Daily Value. See Reading a Protein Powder Label.
Percent Daily Value on labels
FDA explains that a percent Daily Value for protein is required only if a protein claim such as "high in protein" is made, or if the product is meant for infants or children under 4. [7] FDA adds that current evidence indicates protein intake is not a public health concern for US adults and children over 4. [7] When shown, the percentage is based on protein corrected for quality (digestibility-corrected amino acid score). [4] See Protein Quality Scores.What the sources do not settle
The sources we read say "per kg body weight" without telling readers which weight to use for people far above or below a typical weight, so that question is not answered here. For adults 65 and over, Germany's DGE gives 1.0 g/kg/day and separately states grams per day in relation to a reference body weight, so a gram figure and a per-kilogram figure from the same body may not match a given person's own weight. [3] Reference values are for healthy populations. Needs in kidney disease, liver disease, pregnancy, illness or surgery are set by a clinician or dietitian. [8]Frequently asked questions
How many calories are in a gram of protein?
MedlinePlus states that one gram of protein supplies 4 calories. [1]
How do I convert grams per kilogram to grams per day?
Multiply the g/kg value by body weight in kilograms. The result is an illustration of the sum, not a personal target; a clinician or dietitian can say what applies to you. [2]
Are percent of calories and percent Daily Value the same?
No. Percent of calories is protein calories divided by total calories. The Daily Value for protein on US labels is 50 g for adults and children 4 and over, and a percentage of it appears only in certain cases. [7]
Why do Canadian, European and US figures differ?
They come from different bodies, years and methods, for example Health Canada 0.80 g/kg/day and EFSA 0.83 g/kg/day for adults. [2] [3]
Do I need more protein if I exercise or am older?
Some agencies describe higher ranges for older adults; for example the Nordic recommendations suggest 1.2 to 1.5 g/kg for older adults. [3] Individual needs depend on health, so ask a clinician or dietitian, and see Protein Intake Levels.
References
- MedlinePlus Medical Encyclopedia: Protein in diet (U.S. National Library of Medicine). Read 2026-10-22.
- Health Canada, Dietary Reference Intakes tables: reference values for macronutrients (2005 tables). Read 2026-10-22 through the web-fetch tool.
- Knowledge4Policy (European Commission), Dietary recommendations for protein intake for adults and older adults, last updated 31 March 2026; reproduces statements from EFSA 2012, WHO/FAO/UNU 2007, DGE 2019, Nordic Nutrition Recommendations 2023 and ANSES. Read 2026-10-22.
- eCFR, Title 21 CFR 101.9 Nutrition labeling of food (text version dated 2026-10-01). Read 2026-10-22.
- FDA, Daily Value on the Nutrition and Supplement Facts Labels. Read 2026-10-22.
- NIST, Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically. Read 2026-10-22.
- FDA, How to Understand and Use the Nutrition Facts Label. Read 2026-10-22.
- NIDDK, Eating, Diet, & Nutrition for Chronic Kidney Disease. Read 2026-10-22.