Protein Calculator

The protein floor — why 1.6 g/kg is the new consensus

The widely cited Recommended Dietary Allowance of 0.8 g/kg/day was never intended as an optimum. It was set as the intake needed to prevent nitrogen deficiency in a sedentary adult — a population minimum, not a body composition target. The paradigm shifted definitively with the 2018 systematic review and meta-analysis by Stuart Phillips, Robert Morton, and colleagues published in the British Journal of Sports Medicine (Morton et al., BJSM 2018). Pooling 49 randomised controlled trials with 1,863 participants, the analysis found that the dose–response curve for protein's effect on lean mass gains from resistance training plateaued at a mean of 1.62 g/kg/day. Below that point, more protein reliably produced more muscle. Above it, additional grams produced statistically insignificant incremental gains. For any adult doing structured exercise, 1.6 g/kg is now the evidence-backed floor — not a target for athletes, but the starting point for anyone lifting weights recreationally.

In practice, most nutritional guidelines for active adults now use 1.2–1.6 g/kg as the general range, with 1.6 g/kg as the recommended minimum when muscle maintenance or growth is a priority. The old rule of "1 gram per pound of body weight" (~2.2 g/kg) turns out to be a ceiling, not a necessity — and exceeding it offers no measurable additional benefit for most people while simply increasing calories.

When to push higher — cuts, older adults, and athletes

Three situations consistently support protein intakes above the 1.6 g/kg floor. The first is aggressive caloric restriction. During a cut, dietary protein serves a dual function: it provides the amino acid substrate for muscle protein synthesis, and its high thermic effect (20–30% of calories lost to digestion) makes it the most metabolically expensive macronutrient. More importantly, when calories are low, protein is also oxidised for fuel — meaning you need more to sustain the same net retention. The 2014 systematic review by Helms et al. in the Journal of the International Society of Sports Nutrition recommended 2.3–3.1 g/kg of lean body mass for natural athletes in a caloric deficit, which typically translates to 1.8–2.2 g/kg of total body weight for most recreational lifters.

The second context is adults aged 50 and over. Anabolic resistance — a blunted muscle protein synthesis response to a given protein dose and to resistance exercise — is well documented from the fifth decade. The PROT-AGE study group and subsequent consensus papers recommend that adults over 65 consume 1.0–1.2 g/kg at minimum, and up to 1.5 g/kg with regular exercise. Adding a conservative 0.2 g/kg to any baseline target is a well-supported practical adjustment for adults over 50.

The third is elite athletes during competition prep. The Helms 2014 ceiling and the upper bounds from the Morton 2018 analysis converge around 2.2–2.4 g/kg as the practical upper limit where any marginal gains disappear. Beyond 2.4 g/kg, you are simply eating more expensive calories with no measurable body composition advantage.

The kidney myth — what the data actually shows

The most persistent misconception in nutrition is that high protein intake damages healthy kidneys. This concern was extrapolated from nephrology literature: in people with existing chronic kidney disease (CKD), high dietary protein accelerates glomerular filtration pressure and does hasten progression. This is a clinically meaningful finding for CKD patients. It does not apply to people with normal renal function.

The definitive controlled evidence comes from a 2018 randomised trial by Devries et al. published in the Journal of Nutrition. Healthy adults consuming 2.4 g/kg/day of protein for 8 weeks showed no adverse changes in kidney function — GFR, serum creatinine, and blood urea nitrogen all remained within normal ranges. Multiple long-term observational studies in athletes consuming 3 g/kg+ over years show no pathological kidney findings in the absence of pre-existing disease. If your kidneys are healthy, there is no evidence-based rationale for capping intake at any level below 2.4 g/kg on safety grounds.

Per-meal distribution — the leucine trigger

Muscle protein synthesis is not a faucet that stays open as long as amino acids are circulating. It is a threshold-triggered response, primarily gated by leucine — the essential branched-chain amino acid that directly activates the mTOR signalling pathway. The foundational research by Stuart Phillips and colleagues (Phillips & Van Loon, 2009, JISSN) established that approximately 0.4 g/kg per meal is the minimum dose required to maximally stimulate MPS — roughly 25–40 g of protein for most adults. Doses above this threshold produce equivalent MPS responses in young adults (though older adults may benefit from slightly higher per-meal doses due to anabolic resistance).

The practical implication: distributing daily protein across 3–4 meals, each meeting the per-meal threshold, is physiologically superior to consuming the same daily total in two large boluses. A person eating 160 g/day in four 40 g meals will accumulate more total muscle protein over 24 hours than one eating 80 g at breakfast and 80 g at dinner, even though total intake is identical. This is why the calculator shows both 3-meal and 4-meal per-serving breakdowns — and why skipping meals while hitting a daily total is a suboptimal strategy for body composition.

Plant vs animal protein — completeness, DIAAS, and combining

Protein quality is measured by the Digestible Indispensable Amino Acid Score (DIAAS), which evaluates both the amino acid profile and the digestibility of a protein source against the pattern of human requirements. Animal proteins — whey, casein, eggs, chicken, fish — score 1.0 or above, meaning they are complete and highly digestible. Most plant proteins score below 1.0: pea protein scores around 0.82, rice protein around 0.59. Soy is the exception among plants, scoring comparably to dairy (DIAAS ~1.0).

The practical implication for vegans is not that plant protein is inadequate, but that a higher daily total helps compensate for lower digestibility and that food variety matters. Legumes are rich in lysine but low in methionine. Grains are the inverse. Combining sources across the day — lentil soup with rice, tofu with edamame and quinoa — produces a complete amino acid profile. Vegans targeting muscle gain should aim for the upper end of any range (e.g., 2.0 g/kg instead of 1.6 g/kg) to account for the DIAAS gap. Pea-rice protein blends are the most practical supplement choice, as the combination approaches dairy protein's amino acid completeness.

How to actually hit the number

Protein targets that exist only on paper don't build muscle. Here are food equivalents to make the numbers concrete. All values are approximate and refer to cooked weight or prepared serving:

• 100g chicken breast (cooked) — 31g protein
• 100g canned tuna (drained) — 26g protein
• 100g salmon (cooked) — 25g protein
• 30g whey protein powder — 24g protein
• 100g Greek yoghurt (plain, 2%) — 10g protein
• 100g firm tofu — 17g protein
• 100g tempeh — 20g protein
• 1 cup cooked lentils (~200g) — 18g protein
• 1 cup cooked chickpeas (~164g) — 15g protein
• 1 large egg (~50g) — 6g protein
• 30g cheddar cheese — 7g protein
• 240ml whole milk — 8g protein

A practical 160g/day template: 30g whey in the morning (24g protein), 150g chicken at lunch (46g), 200g Greek yoghurt mid-afternoon (20g), 200g salmon at dinner (50g), 1 cup lentils as a side (18g). That totals ~158g — on target with minimal tracking complexity. Photographing meals in CalEye automatically calculates the protein content without weighing individual ingredients.

Related reading

• Protein targets for weight loss — why the RDA is not enough
• The thermic effect of protein — why it burns more than carbs or fat
• Collagen protein is incomplete — what that means for your goals
• Macro calculator — protein, carbs, and fat in grams
• TDEE calculator — total daily energy expenditure

Frequently asked questions

Why is 1.6 g/kg now considered the minimum for active people?

The 2018 systematic review and meta-analysis by Morton et al. in the British Journal of Sports Medicine pooled 49 trials (1,800+ participants) and found that the mean protein intake at which resistance-training gains in lean mass plateaued was 1.62 g/kg/day. Below that threshold, additional protein reliably increased muscle protein synthesis; above it, returns diminished rapidly. The RDA of 0.8 g/kg was derived from nitrogen-balance studies in sedentary adults and represents a floor for preventing deficiency, not an optimum for body composition or performance. For any adult doing structured exercise, 1.6 g/kg is now the evidence-backed floor.

Is eating too much protein dangerous for your kidneys?

No — in healthy adults with no pre-existing kidney disease, high protein intake does not cause kidney damage. The 2018 randomised trial by Devries et al. fed healthy adults 2.4 g/kg/day for 8 weeks with no adverse changes in kidney function markers (GFR, creatinine, BUN). The concern originated from studies in people with existing chronic kidney disease (CKD), where dietary protein does accelerate progression. If you have diagnosed CKD, follow your nephrologist's guidance. If your kidneys are healthy, the evidence does not support restriction below 2.4 g/kg as a safety measure.

Can vegans and vegetarians hit these protein targets?

Yes, with planning. The main challenge is that plant proteins generally have lower DIAAS (Digestive Indispensable Amino Acid Score) than animal proteins — soy is the exception, scoring comparably to whey. Legumes are low in methionine; grains are low in lysine. Combining sources across the day (not necessarily at each meal) fills the amino acid profile. Practical high-protein plant foods: firm tofu (17g/100g), edamame (11g/100g), lentils (9g/100g cooked), chickpeas (9g/100g), tempeh (20g/100g), seitan (25g/100g). Vegan athletes may benefit from targeting the higher end of any recommended range (e.g., 2.0 g/kg instead of 1.6 g/kg) to account for lower digestibility.

Does it matter when I eat my protein, or just the daily total?

Both total and distribution matter. Research by Phillips and colleagues (2009, JISSN) established that muscle protein synthesis requires approximately 0.4 g/kg per meal as a minimum threshold — roughly 25–40 g for most adults — to maximally activate the mTOR signalling pathway via the essential amino acid leucine. Spreading protein across 3–4 meals rather than front- or back-loading it produces meaningfully higher 24-hour MPS rates than two large doses, even at identical daily totals. So hitting 160 g/day in 4 meals of 40 g each is physiologically superior to 160 g in 2 meals of 80 g.

What counts as "1 gram of protein"?

Protein grams refer to the protein macronutrient, not the weight of the food. Protein content varies significantly by source. Per 100g of food: chicken breast (cooked) 31g, canned tuna 26g, whey protein powder 80g, tempeh 20g, Greek yoghurt (plain, 2%) 10g, cooked lentils 9g, whole egg (1 large egg = ~50g) 6g protein. Tracking labels or a photo-logging app accounts for the actual protein content rather than food weight.