Estimate daily protein using body weight and an estimated calorie range. The result compares an illustrative activity-based range with the US adult 10–35% energy range and the WHO safe intake for healthy adults. It is a starting point for understanding the methods, not an individual meal plan.
How to interpret the result
Start with the weight-based figures. The adult RDA is commonly expressed as 0.8 g/kg/day; the Academy of Nutrition and Dietetics lists 46 g/day for adult women and 56 g/day for adult men as standard RDA reference amounts. These describe healthy populations; individual needs can differ. The WHO result is a similar population-level safe intake, not a maximum.
The 10–35% result answers a different question: how many grams would account for that share of estimated daily calories? It can be broad because both the share and the calorie estimate span wide ranges. A result near its upper end is not automatically a recommended target.
For physically active people, published athlete ranges can differ from the illustrative activity comparison. The NIH Office of Dietary Supplements describes research suggesting about 1.2–2.0 g/kg/day for athletes.
A check you can do by hand
For a 70 kg adult, the WHO calculation is 70 × 0.83 = 58.1, shown as 58 g/day. At an estimated 2,000 calories, the adult 10–35% energy range converts to 50–175 g/day because 2,000 × 0.10 ÷ 4 = 50 and 2,000 × 0.35 ÷ 4 = 175. One method starts from weight and the other from estimated energy.
Food portions
Protein in foods depends on the portion and product. As a quick comparison, the Academy's serving examples each provide about 7 g: one egg, one ounce of cooked meat, poultry or fish, half a cup of cooked beans or lentils, or one ounce of nuts or seeds. Check the food label or USDA FoodData Central for a particular item and serving size.
Examples
70 kg adult: weight-based comparison
The illustrative sedentary range is 56–70 g/day. The WHO safe intake rounds to 58 g/day. These weight-based values do not change when the activity factor changes the estimated calories.
2,000-calorie energy example
Ten to 35 percent of 2,000 calories is 200–700 calories from protein. Dividing by 4 kcal/g gives 50–175 g/day. The calculator uses its own estimated calorie value in place of 2,000.
Formula
The default calorie estimate starts with Mifflin St Jeor basal metabolic rate (BMR). The optional Katch-McArdle formula uses body fat to estimate lean mass. Let W be weight in kilograms, H height in centimetres, and A age in years.
Men: BMR = 10W + 6.25H − 5A + 5
Women: BMR = 10W + 6.25H − 5A − 161
Katch: BMR = 370 + 21.6 × W × (1 − body-fat fraction)
Calories = round(BMR × selected activity factor)
The calculator then rounds each daily protein figure to whole grams:
Activity comparison, sedentary: 0.8W–1.0W g
Activity comparison, other: 1.0W–1.8W g
US adult energy range: calories × 10% / 4 to calories × 35% / 4 g
WHO safe intake: 0.83W g
The activity comparison is a calculator scenario, not an official Academy of Nutrition and Dietetics recommendation. The adult energy range is the US acceptable macronutrient distribution range; the conversion uses the USDA general energy factor of 4 kcal per gram of protein. The WHO report describes 0.83 g/kg/day as a safe intake expected to meet the needs of most healthy adults.
Calorie and protein outputs are estimates. The form covers ages 18–80 but does not model pregnancy, nursing, children, kidney or liver disease, or individual medical needs. A registered dietitian or clinician can help set an appropriate target for those situations.