The short answer
If you train and want a number to work with: 1.6g of protein per kilo of bodyweight per day is the evidence-backed baseline for maintaining muscle, 2.0g if you're trying to build it, and 2.2g or more if you're losing fat. A 75kg person who lifts is therefore looking at roughly 120–150g a day.
If you're mostly sedentary, the official UK reference of 0.8g/kg is the floor, not the ceiling — it was set to prevent deficiency, not to optimise anything. Most people who exercise do better above it.
Why grams per kilo beats grams per day
You've probably seen absolute targets like “eat 150g of protein a day.” That number is meaningless without a bodyweight attached: 150g is generous for a 60kg woman and barely adequate for a 100kg man. Protein needs scale with the size of the body being maintained, which is why every serious guideline expresses them per kilo.
So ignore one-size-fits-all gram targets (including ours, if you borrow someone else's). The only number that matters is yours: your weight × the right multiplier. Our protein calculator does exactly that and shows its working.
Where these numbers come from
The 1.6g/kg figure comes from Morton et al. (2018), a meta-analysis of 49 trials with 1,863 participants, which found that protein boosted muscle gains from resistance training up to about 1.6g/kg/day — beyond that, extra protein stopped adding benefit. Read the paper.
The wider ranges come from the International Society of Sports Nutrition's 2017 position stand: 1.4–2.0g/kg/day is sufficient for most exercising people, rising to 2.3–3.1g/kg/day to protect lean mass during a calorie deficit. Read the position stand.
The deficit exception
Dieting changes the maths. When you're in a calorie deficit your body is more inclined to burn muscle along with fat, and protein is the main nutritional defence. That's why the ISSN's range jumps to 2.3–3.1g/kg for people cutting — the leaner you get, the more it matters.
This is the single most underappreciated protein fact in fitness: the people eating the least food need the most protein per kilo. If you're losing fat on 1.2g/kg, you're likely losing muscle with it.
Does gender change the target?
No — not in any official guideline. The German Nutrition Society's reference values state explicitly that because data on gender-specific differences is inconsistent, no separate values for women and men were derived. The g/kg framework already accounts for the main difference, which is body size.
The honest caveat is body composition, not gender: at the same weight, a person with more body fat has less muscle to maintain, so very overweight people may do better targeting a lean-mass-based number. Our calculator flags this in its assumptions.
More is not better
Beyond roughly 1.6–2.2g/kg (depending on goal), extra protein doesn't build extra muscle — it just becomes expensive calories. The Morton analysis is clear on the plateau, and no trial has shown a meaningful advantage to pushing past it for muscle gain.
Two myths to retire: protein doesn't damage healthy kidneys (that's a clinical-population concern misapplied to gym-goers), and you don't need to “cycle” protein. Consistency at the right target beats heroic intake.
Find your number
Pick your weight, goal and activity level and get a daily target with the full equation shown — plus how to split it across meals and which products actually hit it. It takes 30 seconds: try the protein calculator.