How Much Protein You Need Per Day
At 80 kg, the adult reference intake of 0.8 g/kg gives you 64 g of protein a day. The sports-nutrition range of 1.4 to 2.0 g/kg gives you 112 to 160 g. Both figures are correct, because one is a population reference and the other comes from studies of people lifting weights. Treating either as a universal requirement is where most people go wrong.
Reference intake and exercise research
The commonly cited 0.8 g/kg/day deserves better than its reputation as a starvation threshold. It is a population reference, set to cover most adults. Sports-nutrition research examines higher intakes alongside resistance exercise, and the ISSN position stand on protein and exercise describes 1.4–2.0 g/kg/day as sufficient for most exercising individuals in the population it discusses.
The sum is your body weight multiplied by grams per kilogram, and nothing more. It illustrates a published range without settling anything about your personal target. The protein calculator runs every band on this page at once and prints the width of each one, which is the only honest way to show a breakpoint that has uncertainty around it.
What the 1.6 g/kg figure means
The Morton and colleagues, 2018 protein meta-analysis pooled 49 studies of protein supplementation and resistance training in healthy adults and put the breakpoint at about 1.62 g/kg/day, with considerable uncertainty around it. That 1.62 is a statistical estimate across studies, so nobody’s muscle growth switches off at 1.61 and nobody’s training fails below it.
At 80 kg, 1.6 g/kg is 128 g. At four kcal per gram that is 512 kcal, which leaves you the rest of the day’s food to arrange around nutritional quality, preference and any medical needs. The macro calculator does that arranging for you, holding protein at the per-kilogram figure you pick, setting a fat floor, and giving whatever calories remain to carbohydrate.
Food portions need their own labels
Protein content shifts with brand, preparation, water content and serving size, so read the actual food label or a proper food-composition database. A cup of lentils and a cup of rice are not both 30 g, and tofu and yoghurt vary enormously between products.
Spread your protein through the day if that suits how you eat. A four-meal schedule is optional, and absorption does not stop dead at a fixed number of grams per sitting.
Higher intakes need context
Evidence in healthy exercising adults says little about indefinitely high intakes or about everyone else. Kidney disease, pregnancy, illness and older-age nutritional needs all call for proper professional advice. Substituting a goal weight for your current one also moves the answer substantially, so have a reason before you do it.
Protein does not make an aggressive calorie deficit safe, and it will not buy you simultaneous fat loss and muscle gain. Use the calorie tool for energy examples and the deficit guide for their limits. No supplement is required to use anything on this site.
Scope and correction note, 13 September 2026: This guide provides general adult education. It has been revised to distinguish estimates from measurements and to remove unsupported guarantees. It has not received independent clinical review. See the editorial policy and medical disclaimer.