Find your daily protein target

Search "how much protein do I need" and you'll get answers ranging from 50 grams a day to 250. Both numbers appear in real guidelines. Neither is wrong. They're answering different questions.

We built this calculator to answer the specific one: how much protein do you need, given your body weight, how you train, and what you're trying to change. Here's the reasoning behind every number it produces.

The Recommended Dietary Allowance for protein is 0.8 grams per kilogram of body weight per day. For a 180-pound adult, that's about 65 grams.

That figure gets quoted as though it were a goal. It isn't. The RDA is defined as the intake sufficient to meet the requirements of nearly all healthy individuals, roughly 98% of the population (Phillips, British Journal of Nutrition, 2012). It answers "what prevents a deficiency," not "what supports the outcome I want."

There's a second problem. The RDA was derived largely from nitrogen balance studies, a method that research using the more precise indicator amino acid oxidation technique suggests systematically underestimates protein requirements. Reanalysis using that method puts the requirement for sedentary adults closer to 1.2 g/kg. So even the baseline is probably conservative.

The calculator starts above the RDA for that reason. Everyone gets a floor that reflects maintenance, not deficiency prevention.

Two sources do most of the work here.

The International Society of Sports Nutrition's 2017 position stand on protein and exercise concluded that a daily intake of 1.4 to 2.0 g/kg is sufficient for most exercising people to build and maintain muscle (Jäger et al., JISSN, 2017). That range covers a 180-pound person at roughly 115 to 165 grams per day.

The second is a 2018 meta-analysis in the British Journal of Sports Medicine that pooled 49 studies and 1,863 participants to find the point where additional protein stops producing additional lean mass. The breakpoint landed at 1.62 g/kg per day, with a 95% confidence interval running from 1.03 to 2.20 (Morton et al., 2018).

That single study explains most of the confusion in this category. The 1.6 figure is the point estimate. The 2.2 figure is the top of the confidence interval. Both get quoted as "the number," which is how you end up with two credible-sounding answers 35% apart.

In pounds, since most people weigh themselves that way:

Resistance training and endurance training raise protein needs through different mechanisms, and the research treats them separately.

For lifting, the driver is muscle protein synthesis: training creates the stimulus, and dietary protein supplies the substrate. The two work together, which is why the ISSN describes exercise and protein intake as synergistic rather than additive.

For endurance work, the driver is amino acid oxidation. You burn a meaningful amount of protein during prolonged aerobic exercise, and you have to replace it. Consensus guidelines have long put endurance athletes at 1.2 to 1.4 g/kg. More recent work using indicator amino acid oxidation found a recommended intake of 1.83 g/kg on a high-volume training day, well above that range (Kato et al., PLOS One, 2016).

The practical takeaway: a marathoner in peak training needs more protein than most endurance guidelines suggest, and roughly as much as a lifter. The calculator's activity tiers reflect training volume, not training style, for that reason.

This is the part most calculators get backwards. People assume building muscle requires the most protein. Losing fat often requires more.

When you eat in a calorie deficit, your body becomes more willing to break down muscle tissue for energy. Higher protein intake pushes back against that. The ISSN position stand notes that intakes of 2.3 to 3.1 g/kg may be needed to maximize lean mass retention in resistance-trained people during hypocaloric periods.

One honest caveat on that figure: the underlying review expressed it relative to fat-free mass rather than total body weight, and the distinction matters a lot at higher body fat percentages. A 300-pound person and a 180-pound person with the same lean mass have similar protein requirements, even though a body-weight formula would tell them otherwise. The calculator caps the combined multiplier for this reason, and if your body fat is well above average, treat the result as an overestimate.

Muscle protein synthesis becomes less responsive to protein with age, an effect usually described as anabolic resistance. The same 25-gram serving does less for a 70-year-old than a 30-year-old, which means the RDA is a particularly poor target for older adults.

The PROT-AGE study group, convened by the European Union Geriatric Medicine Society, recommends 1.0 to 1.2 g/kg per day for adults over 65, and at least 1.2 g/kg for those who are exercising or otherwise active (Bauer et al., JAMDA, 2013). The Morton meta-analysis found the same thing from the other direction: the benefit of protein supplementation decreased as participant age increased.

Every input to this calculation carries uncertainty. Your body weight is precise. Your training volume is an estimate. The research itself reports confidence intervals rather than points.

A calculator that returns "137 grams" implies a precision that doesn't exist. We show a range because that's how the underlying evidence is actually reported, and because anywhere inside a well-constructed range will work. Aim for the middle. Move toward the top during a deficit or a heavy training block.

Total daily intake matters most. Distribution matters second, and it isn't negligible.

The ISSN recommends 0.25 g/kg per serving, or an absolute dose of 20 to 40 grams, spaced every three to four hours across the day. Each dose should deliver 700 to 3,000 mg of leucine alongside a full spread of essential amino acids, since leucine is the amino acid that triggers the synthesis response.

For a 180-pound person eating four times a day, that's roughly 20 grams per meal to reach 80, or 35 grams per meal to reach 140. Most people distribute this poorly: a light breakfast, a moderate lunch, and 60 grams at dinner produces a worse result than the same total spread evenly.

Whole food should do most of the work. Supplementation exists to close the gap, particularly when your target is high enough that four large protein servings become impractical, or when you're managing total calories at the same time.

This tool gives you a defensible starting range. It doesn't replace a dietitian if your situation is complicated.