How much protein do you really need to build muscle?

For someone doing resistance training to gain muscle, the evidence points to a daily protein intake of about 1.6 grams per kilogram of bodyweight — around 112 grams a day for a 70-kilogram person [s1]. That is roughly double the official minimum, and, importantly, the data suggest eating much more than it buys little extra muscle [s1].

The number worth knowing is not the government's, and not the supplement label's. It comes from pooling the trials that actually measured muscle.

Where 1.6 comes from

The single most-cited figure in this area is a 2018 meta-analysis in the British Journal of Sports Medicine that combined 49 randomised trials with 1,863 participants, all doing resistance training for at least six weeks [s1]. Adding protein produced real but modest average gains: fat-free mass rose by 0.30 kg more than in control groups (95% confidence interval 0.09 to 0.52), and one-repetition-maximum strength by 2.49 kg (0.64 to 4.33) [s1].

The more useful part was a break-point analysis of total daily intake. Benefits to fat-free mass increased as intake rose, then stopped: beyond a total protein intake of about 1.62 g/kg/day, extra protein added no further training gains [s1]. That is the origin of the "1.6 grams" rule of thumb now repeated across gyms — and it is a ceiling on the useful dose, not a floor.

A sports-nutrition consensus lands in the same region from a different direction. The International Society of Sports Nutrition's 2017 position stand concludes that an intake of 1.4 to 2.0 g/kg/day is sufficient to build and maintain muscle for most people who exercise [s2]. The overlap between an evidence synthesis that found a plateau near 1.6 and a guideline range of 1.4 to 2.0 is the closest thing this field has to a settled answer.

Why it is far above the "official" number

The protein figure most people have heard — 0.8 g/kg/day, about 56 grams for a 70-kilogram adult — comes from the National Academies' Dietary Reference Intakes [s4]. But that value is defined as the amount that prevents deficiency in nearly all healthy adults [s4]. It answers "how little can I get away with," not "how much supports building muscle," which is why the training literature sits roughly twice as high, as our explainer on general protein needs lays out.

Total intake matters more than timing

A recurring anxiety is that protein has to be timed precisely — a post-workout "window." The stronger signal in the data is that the daily total, spread reasonably through the day, is what counts, a point covered in our look at the anabolic-window question. A 2018 review on per-meal distribution recommends aiming for about 0.4 g/kg per meal across a minimum of four meals to reach at least 1.6 g/kg/day [s3]. Muscle protein synthesis from a single serving of fast-digesting protein appears to be maximised around 20 to 25 grams in young adults, which is one reason the guidance favours spreading intake rather than loading it into one or two large servings [s3]. The ISSN puts a typical per-serving target near 0.25 g/kg, or an absolute 20 to 40 grams [s2].

The caveats that change the target

Two findings move the number for real people. First, age blunts the effect: in the meta-analysis, the benefit of added protein to fat-free mass shrank as participants got older [s1] — consistent with the separate case that older adults need more protein, not less, to hold muscle. Second, training status cuts the other way: the response to supplemental protein was actually larger in people who were already resistance-trained [s1], so the beginner who "doesn't need much yet" has it backwards.

Dieting is the main scenario where intakes push above 2.0. To hold onto lean mass while eating at a calorie deficit, the ISSN cites evidence for 2.3 to 3.1 g/kg/day [s2] — a specialised case, not a general recommendation, and one where the goal is preserving muscle rather than building it.

What this means

For a healthy adult lifting weights and eating enough calories, roughly 1.6 g/kg/day is a well-supported target, and there is little evidence that pushing far beyond it builds extra muscle [s1][s2]. Higher figures belong to specific situations — dieting to preserve lean mass — rather than to everyone [s2]. The persistent claim that ordinary gym-goers must chase 2 grams per pound (well over 4 g/kg) has no support in the pooled trials [s1]. This is informational only, not dietary advice; anyone with kidney disease or another condition that limits protein should follow their own clinician, and the specific worry about protein and healthy kidneys is addressed in our review of that question.