"How much protein?" gets a different answer from everyone, because the question has at least three versions: how much do you need to avoid a deficiency, how much helps you build muscle, and how much is worth eating for everything else you care about. The research gives ranges for each. This article walks through the main sources, and what they do not say. The protein calculator turns them into grams for your weight.
The floor: 0.8 grams per kilogram
The US Recommended Dietary Allowance for adults is 0.8 grams of protein per kilogram of body weight a day. It was set to meet the needs of nearly all healthy adults, which makes it a floor for avoiding deficiency, not a goal for people who train.
For exercising people: about 1.4 to 2.0 grams per kilogram
The International Society of Sports Nutrition's 2017 position stand concluded that about 1.4 to 2.0 grams per kilogram a day is enough for most exercising people to build and keep muscle. That is roughly 1.75 to 2.5 times the RDA.
For building muscle: gains level off near 1.6
A 2018 meta-analysis in the British Journal of Sports Medicine pooled 49 randomized trials with 1,863 people doing resistance training. It found that protein intake beyond about 1.6 grams per kilogram a day did not add further fat-free mass gains on average. The confidence interval around that break point was wide: from about 1.0 to 2.2 grams per kilogram. That is why the calculator's muscle-building range runs from 1.6 to 2.2: 1.6 is where the average benefit leveled off, and 2.2 is the top of the uncertainty. The same analysis found the benefit was smaller in older people and larger in people with more training experience.
In a calorie deficit
The same position stand noted that lean, resistance-trained people eating below maintenance may need more, about 2.3 to 3.1 grams per kilogram a day, to hold on to as much muscle as possible. That evidence is for people who already lift and are already lean. It is not a general recommendation, and it does not mean everyone who is dieting should eat that much.
What the research does not say
- It does not say more is always better. Gains level off, and protein has to fit with the rest of what you eat.
- These ranges are per kilogram of total body weight. People with a lot of extra body fat may find them high, and a dietitian can tailor it.
- They are for healthy adults. They are not advice for pregnancy, kidney disease or anyone on a medically supervised diet.
How Vital uses it
Vital's protein setting offers Standard (about 1.6 g/kg), High (about 2.0 g/kg) and Very high (about 2.4 g/kg), so a person picks where in the range they want to sit. The target is a number you can edit at any time, and the app tracks your protein against it each day. It is a target for tracking, not a medical recommendation.
Sources
- Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005. doi:10.17226/10490
- Jager R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr 2017;14:20. doi:10.1186/s12970-017-0177-8
- Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med 2018;52(6):376-384. doi:10.1136/bjsports-2017-097608
Written November 5, 2026. This is general information, not medical advice. Talk to a doctor or dietitian before big changes to how you eat or train, especially with a medical condition or a history of disordered eating.