How this instrument works
Protein is the one macronutrient the body cannot stockpile against a future shortage, so a supply has to arrive each day — and the amount that counts as enough scales with how much tissue there is to keep in repair. That is why the target is a multiplication rather than a flat number of grams. The floor is the Recommended Dietary Allowance of 0.8 grams per kilogram of body weight, the intake at which nitrogen balance holds steady in almost every healthy sedentary adult. Run a 70 kg body through it and you get 56 grams a day, which is exactly the figure printed in the reference tables.
Training pushes the coefficient up, for two separate reasons. Resistance work tears down myofibrillar tissue and then rebuilds it at an elevated rate for a day or more afterwards; endurance work oxidises a small share of amino acids outright as fuel, and oxidises more of them the longer the session runs. Position stands from sports-nutrition bodies converge on 1.2 to 2.0 g/kg for people training seriously, which is where the 1.2, 1.6, and 2.0 settings on the dial come from. Past roughly 2 g/kg the surplus is mostly burned for energy rather than built into muscle.
Two things the multiplication cannot see. It uses total body weight, which overshoots for anyone carrying a lot of fat mass — lean tissue does the maintaining, so a lean-mass basis of about 1.6 to 2.2 g per kg of lean tissue tracks better above roughly 30% body fat. And it returns a daily total, not a schedule: three or four servings of 25 to 40 grams stimulate muscle synthesis more effectively than banking the whole allowance on one enormous dinner.
- Set Body weight — kilograms, pounds, or stone; the unit menu converts before the multiplication runs.
- Pick the Activity level that matches an ordinary week rather than your best one: sedentary 0.8, active 1.2, strength training 1.6, endurance 2.0 g/kg.
- Read Protein (g/day) — the whole-day total from all food and drink, rounded to the nearest gram.
- Spread that total across three or four meals of 25 to 40 grams instead of loading it onto a single sitting.
- Revisit the figure whenever body weight or weekly training load shifts appreciably; both inputs drift over a season.
Worked example — 70 kg, training four days a week
Take a 70 kilogram adult who lifts or runs four mornings a week — the Active setting, 1.2 grams per kilogram. The arithmetic is a single line: 70 × 1.2 = 84 grams a day. Against the sedentary floor of 70 × 0.8 = 56 grams, that is 28 extra grams, a gap about the size of one chicken breast.
Split across the day, 84 grams arrives as roughly 30 g at breakfast (two eggs plus a 170 g pot of Greek yoghurt), 30 g at lunch (a 120 g tin of tuna with beans), and 24 g at dinner — before the bread, rice, or pasta on the side contributes its own quiet share. Nothing exotic is needed to reach it, which is the useful thing to establish before anyone buys a tub of powder.
Questions
How many grams do I need per day?
Multiply your body weight in kilograms by 0.8 if you are sedentary, 1.2 if you train a few times a week, 1.6 if you lift seriously, and 2.0 for heavy endurance training. A 70 kg adult therefore lands somewhere between 56 and 140 grams a day depending on the load. The 0.8 coefficient is a floor set to prevent deficiency rather than a performance target, so anyone training regularly is usually better served nearer the middle of that range.
Should I use total body weight or lean body mass?
Total body weight works for most people and is what this sheet takes. It overstates the requirement for anyone well above about 30% body fat, because fat tissue needs almost nothing to maintain while muscle does the actual work. If that describes you, a lean-mass basis of roughly 1.6 to 2.2 g per kg of lean tissue — or total weight at a goal figure rather than today's — gives a more honest target.
Can a high-protein diet damage healthy kidneys?
There is no evidence that it does in people with normal kidney function; controlled trials running at 2 g/kg and above have not shown harm to glomerular filtration in healthy adults. Existing kidney disease is the genuine exception, and there intake is deliberately restricted and set by a clinician rather than by any calculator. Drink enough water either way, since clearing the extra nitrogen as urea costs fluid.
How much can the body use in one meal?
Roughly 0.4 grams per kilogram per sitting, or about 25 to 40 grams for most adults, saturates the muscle-building response to a single serving. Anything beyond that is not wasted — it is still absorbed and still counts toward the daily total — but the surplus goes toward energy and other tissues instead of extra muscle. Four servings of that size is the practical route to a target near 100 grams.
What does 84 grams look like on a plate?
About 100 g of cooked chicken breast carries 30 g, a large egg about 6 g, 100 g of lentils around 9 g, a 170 g pot of Greek yoghurt 15 to 17 g, and 100 g of firm tofu close to 17 g. Two of those at each of three meals clears 84 g without much planning. Bread, oats, rice, and pasta quietly add 5 to 10 g per serving, which is why mixed diets tend to reach the sedentary floor without anyone aiming at it.
Do older adults need more?
Yes — the working consensus for adults past about 65 is 1.0 to 1.2 g/kg rather than 0.8, because ageing muscle responds less strongly to the same dose of amino acids. Choosing Active instead of Sedentary is a fair approximation for an older adult in good health. Pregnancy and breastfeeding raise the requirement too, by roughly 25 grams a day through the second and third trimesters.
References
- NIH Office of Dietary Supplements — Nutrient Recommendations and Databases (DRIs)
- National Academies — Dietary Reference Intakes for Protein and Amino Acids (2005)
- USDA and HHS — Dietary Guidelines for Americans
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.