Various figures circulate, from "everyone already eats enough" to schemes of three grams per kilogram of body weight. Below is what is used in practice and how to work it out for yourself.
The baseline for people who do not train
For adults who do not exercise intensively, the general guideline is around 0.8 grams of protein per kilogram of body weight per day. That is the amount needed to prevent deficiency, not the amount that is optimal for someone who trains.
What you need if you train
If you exercise regularly, your requirement is higher. For people who train, 1.4 to 2.2 grams per kilogram of body weight is generally used.
Where you land within that range depends on two things: how hard you train and what your goal is. If you are building muscle mass, or training while in a calorie deficit, you sit at the upper end. That last point matters more than many people realise: precisely when losing weight you want to keep protein intake high, because otherwise you lose muscle mass alongside fat.
If you weigh eighty kilos and train seriously, you end up between 110 and 175 grams a day.
More is not better
Above that range research shows no further benefit for building muscle. The surplus is simply burned or stored, just like other nutrients. Anyone going above 2.2 grams per kilogram is mainly paying more for the same result.
What that means on a plate
This is where it becomes practical. 175 grams of protein a day sounds abstract, but amounts to roughly six eating occasions each with a decent portion of meat, fish, dairy, eggs or pulses.
That is perfectly doable if you have time to cook and your day accommodates it. On a busy working day, between appointments or straight after training, it is considerably harder. That is where the practical value of a protein shake lies: it fills a gap you cannot always close with solid food.
That makes it a supplement, not a replacement. Most of your protein should come from ordinary food, if only because there is more in it than protein alone.
How much do you really need?
Grams of protein per kilo of body weight, per day.
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