How much protein do you really need? What the research says, in grams

The baseline: 0.8 g per kg

The RDA of 0.8 g/kg/day comes from nitrogen-balance studies and is set to cover 97.5% of healthy adults. For a 70 kg adult that is 56 g — roughly two chicken breasts, or a tin of tuna plus a cup of lentils and a glass of milk. It is a floor, not an optimum, and it assumes you are not trying to change your body.

Training or losing fat: 1.4–2.2 g per kg

The International Society of Sports Nutrition position stand recommends 1.4–2.0 g/kg for people doing regular exercise who want to build or maintain muscle. A 2018 meta-analysis of 49 resistance-training trials found gains plateaued at about 1.6 g/kg, with the upper confidence limit around 2.2 g/kg — which is why 1.6–2.2 is the range most coaches use.

During a calorie deficit the need rises, because protein protects muscle while fat is lost. Lean, resistance-trained people cutting weight may benefit from 2.3–3.1 g per kg of fat-free mass. For most dieters, 1.8–2.2 g/kg of body weight is a reasonable, achievable target.

Older adults: 1.0–1.2 g per kg

Muscle becomes less responsive to protein with age (“anabolic resistance”). The PROT-AGE study group recommends 1.0–1.2 g/kg for healthy adults over 65, and 1.2–1.5 g/kg for those with acute or chronic illness, combined with resistance exercise where possible.

Per meal, not just per day

Muscle protein synthesis is maximised by roughly 0.25–0.40 g/kg per meal (about 20–40 g for most adults), repeated every three to four hours. Spreading 140 g over four meals of 35 g is more effective than 20 g at breakfast and 100 g at dinner. This is why CalculatorCamp’s protein calculator shows a per-meal figure.

• Chicken breast, cooked, 100 g ≈ 31 g protein
• Eggs, 2 large ≈ 12–13 g
• Greek yoghurt, 170 g ≈ 17 g
• Lentils, cooked, 1 cup ≈ 18 g
• Whey protein, 1 scoop ≈ 20–25 g
• Tofu, firm, 100 g ≈ 15–17 g

Worked examples

• Sedentary office worker, 65 kg, no training: 0.8–1.0 g/kg → 52–65 g/day.
• Recreational lifter, 80 kg, building muscle: 1.6–2.2 g/kg → 128–176 g/day (32–44 g per meal over four meals). The protein calculator’s ‘active + build muscle’ setting gives 1.8 g/kg = 144 g.
• Dieter, 90 kg, losing fat with resistance training: 1.8–2.2 g/kg → 162–198 g/day.
• Healthy 70-year-old, 70 kg: 1.0–1.2 g/kg → 70–84 g/day.

Plant vs. animal protein

Animal proteins (meat, dairy, eggs, whey) contain all essential amino acids in high proportions and are digested efficiently. Most single plant proteins are lower in one or more essential amino acids — grains in lysine, legumes in methionine — and slightly less digestible. That does not make a plant-based diet inadequate; it means variety matters and the total should sit toward the top of the range.

Practical rules for vegetarians and vegans: combine legumes with grains across the day (they do not need to be in the same meal), lean on soy, pea and mixed plant protein powders which have complete profiles, and aim for roughly 10–20% more total protein than the omnivore target — e.g. 1.8–2.4 g/kg instead of 1.6–2.2 when building muscle. Leucine, the amino acid that triggers muscle protein synthesis, is the one to watch: about 2.5–3 g per meal, which is 30–40 g of most plant proteins versus 20–25 g of whey.

Does timing matter?

Less than the supplement industry suggests. The “anabolic window” after training is several hours wide, not 30 minutes, and total daily intake spread over regular meals accounts for almost all of the effect. Two habits do have evidence behind them: eating protein at breakfast rather than back-loading it into dinner, and a 30–40 g serving of slow-digesting protein (casein, Greek yoghurt, cottage cheese) before bed if you train hard and struggle to hit your daily total.

Is high protein safe?

In people with healthy kidneys, intakes up to about 2 g/kg — and in trained populations higher — have not shown harm in controlled trials. People with existing kidney disease are different: protein restriction may be part of their treatment and they should follow their nephrologist’s advice rather than any calculator.