Somewhere between 1.6 and 2.2 grams per kilogram of bodyweight per day. That is the whole answer. Everything below is why, and what to do when hitting it is inconvenient.
Why the range is a range
Muscle protein synthesis stops responding meaningfully to additional intake at around 1.6 g/kg for most people. The upper end of the range exists as a buffer — for a calorie deficit, where protein needs rise because the body is more willing to break down lean tissue, and for people training hard and often.
Going above 2.2 g/kg is not harmful for a healthy person. It is simply not doing anything, while making the rest of your diet harder to fit in.
Why it matters more in a deficit
- It preserves lean mass. Weight lost as muscle is weight you did not want to lose.
- It is the most satiating macronutrient. Adherence to a deficit is mostly a hunger problem, and protein is the cheapest available lever.
- It has the highest thermic effect. A real but small factor — worth knowing, not worth planning around.
If you eat mostly vegetarian
Aim for the upper end rather than the lower, because plant proteins are generally lower in leucine and less completely digested. In practice that means anchoring meals on dairy, soy, legumes and eggs if you eat them, and treating grains and vegetables as the accompaniment rather than the source.
Indian vegetarian eating makes this easier than most cuisines, not harder — paneer, curd, dal and soy chunks are all already in the rotation. The usual gap is breakfast, which tends to be almost entirely carbohydrate.