How much protein you actually need to build muscle

Two claims have sold more protein powder than any gym ever has. The first: you have a narrow window after training, maybe 30 minutes, and if you miss it the workout is wasted. The second: you need 2 grams of protein per kilo of body weight, minimum, or you will never grow. Both are everywhere on fitness social media, and both fall apart the moment you read the actual studies.

This article does one thing: it gives you the real numbers for protein and muscle, separated from the marketing. How much you need, whether timing matters, and why a 28-year-old, a 45-year-old, and a 68-year-old can use almost the same rule. If you want your own figure now, the macro calculator turns your weight and goal into a protein target in about half a minute.

The number that actually matters: about 1.6 g/kg

The single most useful figure in this whole topic comes from a 2018 meta-analysis in the British Journal of Sports Medicine (PMID 28698222). Pooling 49 studies, the researchers found that muscle and strength gains from resistance training kept improving as protein rose, until intake hit roughly 1.6 grams per kilogram of body weight per day. Above that, the extra protein added almost nothing.

For a 75 kg person, 1.6 g/kg is about 120 grams a day. For a 60 kg person it is around 96 grams. That is well within reach of normal food, and it is a long way below the 2.2 g/kg the supplement industry likes to quote. The higher number is not dangerous; it is just not doing what the label implies.

The contrast with everyday needs is worth seeing. The general adult requirement set by the Institute of Medicine in 2005 is 0.8 g/kg, enough to prevent deficiency. Someone training to build muscle needs roughly double that, but not triple, and the curve flattens hard once you reach the muscle-building target.

Timing matters far less than the total

Now the anabolic window. The story goes that muscle protein synthesis spikes briefly after lifting and you must feed it immediately. The reality, measured directly, is that the elevated muscle-building response after a workout lasts at least 24 hours, not 30 minutes.

A 2013 meta-analysis by Schoenfeld and colleagues (PMID 24299050) tested this head-on. When studies matched total daily protein between groups, the timing of protein around the session had no meaningful effect on muscle size or strength. The apparent “window” benefit in earlier work came mostly from the timed group eating more protein overall, not from the clock.

In plain terms: if you train at 7 a.m. and eat a normal protein breakfast at 8, or even lunch at noon, you have not lost the session. What you eat across the whole day is the lever. The minute hand is not.

How to actually hit the target

Knowing the number is easy. Reaching it without thinking about it all day takes a simple structure.

1. Find your target. Multiply your weight in kilograms by 1.6 for muscle gain. A dieter protecting muscle might use 1.8-2.2; a healthy older adult, 1.0-1.2 and up. The macro calculator does this and splits the rest into carbs and fat.
2. Spread it across 3-4 meals. Each serving of 25-40 g triggers a fresh muscle-building response. Even distribution beats loading it all at dinner, a small effect the evidence modestly supports.
3. Anchor each meal with a protein source. Eggs, dairy, chicken, fish, beans, lentils, tofu. If a meal has no obvious protein, that is the gap to fix.
4. Use powder only as a tool, not a rule. A shake is convenient when whole food is hard to reach. The 2018 meta-analysis found supplements help only when total protein is otherwise too low.
5. Set calories first. Protein cannot do its job if your energy is wrong. The BMR & TDEE calculator gives the energy base your macro split sits on top of.

Source matters less than you have been told

Whey gets the marketing because it digests fast and is rich in leucine, the amino acid that flips the muscle-building switch. Per gram, it does edge out most plant proteins. But the practical gap is small, and it closes once you look at a whole day rather than a single shake.

The International Society of Sports Nutrition position stand (2017) is clear on this: people eating plant-based diets reach the same results by taking in slightly more total protein and combining sources so the full range of amino acids is covered. A bowl of lentils and rice, a tofu stir-fry, a bean chilli with cheese, all do the job. The deciding factor is whether you reach your daily target, not whether the protein came from a cow or a soybean.

Age changes the floor, not the rule

The same target applies across most of adult life, with one important shift. After about 60, muscles respond less strongly to each gram of protein, a phenomenon called anabolic resistance. The body needs a bit more to get the same signal.

This is why many experts recommend healthy older adults aim higher than the 0.8 g/kg general RDA, often 1.0-1.2 g/kg or more, especially when combined with resistance training. For a 70-year-old, that combination is one of the most effective tools against sarcopenia, the slow loss of muscle that drives frailty and falls. The rule does not get more complicated with age. The floor just rises.

The takeaway

Strip away the marketing and protein for muscle is almost boring. Aim for around 1.6 grams per kilo of body weight a day. Spread it across a few meals. Do not panic about the clock after training, because the window is closer to a day than to half an hour. Eat a little more if you are over 60 or dieting, and let the source be whatever you will actually eat consistently. The expensive part of building muscle was never the protein. It was the training and the patience.