Protein Calculator guide
Work out how many grams of protein you need per day for your goal, from the 0.8 g/kg RDA minimum to the 1.6-2.2 g/kg range used for building muscle, with the math shown.
The formula: grams per kilogram, not a flat number
Protein needs scale with body size, so every credible recommendation is written in grams per kilogram of body weight per day (g/kg/day). The calculator converts your weight to kilograms (pounds × 0.4536) and multiplies by a factor for your goal. That is the whole formula. The hard part is picking the right factor, and that is where most protein calculators get lazy.
The factors used here come from four sources. The RDA of 0.8 g/kg is the Institute of Medicine's Dietary Reference Intake (2005): the amount that covers the basic needs of nearly all healthy, mostly inactive adults. It is a floor, not a target. The International Society of Sports Nutrition position stand (Jäger et al., 2017) puts 1.4-2.0 g/kg as sufficient for most exercising people to build and keep muscle, and 2.3-3.1 g/kg for resistance-trained people who want to hold on to muscle while dieting. A 2018 meta-analysis in the British Journal of Sports Medicine (Morton et al., 49 studies, 1,863 people) found that gains in muscle from protein plateau around 1.6 g/kg, with the upper confidence limit near 2.2 g/kg. For adults over 65, the PROT-AGE Study Group (Bauer et al., 2013) recommends at least 1.0-1.2 g/kg to slow age-related muscle loss.
Worked example
A 180 lb person who lifts weights to build muscle: 180 × 0.4536 = 81.6 kg. At 1.6-2.2 g/kg, the target is 81.6 × 1.6 = 131 g up to 81.6 × 2.2 = 180 g per day. The RDA for the same person is only 65 g, which shows how far the minimum sits below what training people use.
Split across four meals, the middle of that range (about 155 g) is roughly 39 g per meal. That lines up with the ISSN's per-meal guidance of about 0.25 g/kg or 20-40 g of high-quality protein, spread every 3-4 hours.
When to use goal weight instead
g/kg factors were studied mostly in people of average build. If your BMI is 30 or higher, multiplying total body weight by 2 g/kg gives a number that is high and hard to eat. Enter a realistic goal weight in the optional field and the calculator uses it instead. A 240 lb person aiming for 170 lb gets 123 g at 1.6 g/kg instead of 174 g. That is still plenty to protect muscle during weight loss.
Common mistakes
Treating the RDA as optimal. 0.8 g/kg prevents deficiency. It was never designed for people who train, diet, or are older.
Counting food weight as protein weight. A 6 oz chicken breast weighs 170 g but has about 50 g of protein. Check the protein line on the label or a nutrition database.
Loading it all into dinner. Muscle protein synthesis responds to each meal, so three to five evenly sized protein doses beat one huge one.
Chasing 1 g per pound when cutting is not the issue. 1 g/lb is 2.2 g/kg, the top of the useful range for most people. It is fine, just not required. Dropping to 1.6 g/kg saves money and room for other foods with little downside.
Ignoring total calories. Protein supports muscle, but muscle gain still needs training and enough energy. Use the TDEE or macro calculator to set calories first.
Who should check with a doctor first
People with chronic kidney disease are often told to limit protein, sometimes below the RDA, so do not follow a high-protein target without your nephrologist or dietitian. The same goes for anyone with diabetes and reduced kidney function, liver disease, or certain metabolic disorders. Pregnancy and breastfeeding raise protein needs (the pregnancy RDA is about 1.1 g/kg in the second half), and those targets should come from your prenatal care team. For healthy adults, intakes up to about 2 g/kg have not been shown to harm kidney function.
Hitting the number with real food
Rough protein per serving: 3 oz chicken, turkey, or lean beef 22-26 g; 3 oz canned tuna or salmon 20 g; 1 cup Greek yogurt 20-23 g; 1 cup cottage cheese 25 g; 2 large eggs 12 g; 1 cup cooked lentils 18 g; 3.5 oz firm tofu 12-17 g; a scoop of whey 20-25 g. Build each meal around one of these and the target stops being a math problem.
Protein powder is convenient, not magic. It helps when you are short on time or appetite. Whole foods bring fiber and micronutrients powders do not.
How we calculate: sources
Frequently asked questions
How much protein do I need per day?
The RDA is 0.8 g per kg of body weight (about 0.36 g per lb), which prevents deficiency in inactive adults. People who exercise regularly do better at 1.4-2.0 g/kg, according to the International Society of Sports Nutrition.
How much protein do I need to build muscle?
A 2018 meta-analysis found muscle gains from protein level off around 1.6 g/kg per day, with some people benefiting up to about 2.2 g/kg. That is roughly 0.7-1 g per pound.
Should I eat more protein when losing weight?
Yes, if you lift weights. The ISSN notes 2.3-3.1 g/kg may help resistance-trained people keep muscle during a calorie deficit. For most dieters, 1.6-2.2 g/kg is a practical target.
How much protein should I eat per meal?
About 0.25 g/kg or 20-40 g of high-quality protein per meal, spread every 3-4 hours, is the ISSN's general guidance. The calculator splits your daily target across four meals.
Do older adults need more protein?
Yes. The PROT-AGE Study Group recommends at least 1.0-1.2 g/kg per day for healthy adults over 65 to limit age-related muscle loss, and more for those who are ill or frail.
Is a high-protein diet bad for your kidneys?
In healthy adults, intakes up to about 2 g/kg have not been shown to harm kidney function. If you have chronic kidney disease, follow your doctor's protein limit; this estimate is not medical advice.
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Is 1 gram of protein per pound too much?
For most healthy adults it is safe but more than needed. 1 g per pound equals 2.2 g/kg, the upper end of where muscle-building benefits level off. 0.7 g per pound (about 1.6 g/kg) covers most lifters.
Should I use lean body mass for protein?
Lean mass works if you know it accurately, but most people do not. Using goal weight when BMI is 30 or higher is a simpler way to avoid overestimating.