Protein calculator for weight loss

By Replete · Updated October 27, 2026

Multiply your weight in kg by 1.2 to 1.6 (in pounds, by 0.54 to 0.73), the 2025 to 2030 Dietary Guidelines range, and aim higher the more you exercise. At 160 lb (73 kg), that's 87 to 116 g a day. Eating less doesn't lower it. BMI over 30? Use the weight you'd be at a BMI of 30.

How does this protein calculator work?

It multiplies your weight by a number of grams per kg that rises with how often you exercise. The steps are the ones the Replete app uses to set your protein target:

The range is the Dietary Guidelines' 1.2 to 1.6 g per kg. For people who exercise, the International Society of Sports Nutrition (ISSN) says 1.4 to 2.0 g per kg (0.64 to 0.91 g per lb) is enough for most. Every step is well above the National Academy of Medicine's minimum of 0.8 g per kg, which is a floor to keep from falling short, not a target.

Then one limit: if your BMI is over 30, the calculator uses the weight you'd be at a BMI of 30 for your height. That's 30 times your height in meters, squared; in pounds, 30 times your height in inches, squared, divided by 703.

Say you're 5 ft 7 in (170 cm), weigh 210 lb (95 kg) and exercise 3 to 5 days a week. Your BMI is about 33, so the calculator uses the weight at a BMI of 30 for your height, about 191 lb (87 kg): 87 × 1.6 = 139 g a day, or about 46 g at each of 3 meals. Without the limit it would be 152 g.

Why does the number stop at a BMI of 30?

Because a heavier body doesn't need protein in step with the scale. A 2025 review of protein needs in obesity suggests at least 1.2 g per kg a day during weight loss, with body weight counted only up to a BMI of 30. No trial has tested that directly, so it rests on indirect evidence, but it keeps the number sensible: at 5 ft 7 in and 250 lb (113 kg), the top of the guideline range comes to 139 g a day instead of 181 g.

The calculator doesn't ask for your body fat. You may not know it, and the BMI limit needs only your height and weight.

Does protein go down when you eat less?

No. Eating less cuts calories, not protein: keep the grams where they are and take the cut from fat and carbs. That's why the calculator asks for your weight, not your calories. Set protein as a share of calories instead and it falls just when it matters: 30% of 2,000 kcal is 150 g, but 30% of 1,500 kcal is about 113 g.

It matters because eating less costs some muscle along with the fat, and protein helps you keep it. In 24 trials of reduced-calorie diets, people on higher-protein diets kept about 0.4 kg (1 lb) more lean mass than those on standard-protein diets.

It's not a macro calculator: it works out protein alone.

How much protein per meal?

Divide the day's total by your meals: the calculator shows 3 and 4. If you're building muscle, a 2018 review suggests about 0.4 g per kg at each of at least 4 meals, which adds up to 1.6 g per kg a day, and the ISSN suggests 20 to 40 g a serving, every 3 to 4 hours. More on spreading it out, and the foods that get you there, in protein for weight loss.

Is it different for women, or after 40, 50 or 60?

No. The Dietary Guidelines give one range for adults, not one for each sex or age, so the calculator doesn't ask. Menopause doesn't change it either: no guideline on this page sets a separate figure for it. Over 65, the PROT-AGE expert group recommends at least 1.0 to 1.2 g per kg a day for healthy older adults, and at least 1.2 if you're active: the calculator's lowest step, 1.2, already meets it. For why protein matters more from your 40s, see how much protein women over 40 need.

What if you're trying to build muscle?

Pick how often you train: 6 or 7 days a week gives 1.8 g per kg, inside the ISSN's 1.4 to 2.0. Past a point, more doesn't help: in 49 trials with 1,863 people doing strength training, extra protein added muscle up to about 1.6 g per kg (0.73 g per lb) a day, with no clear gain past that. The popular "1 g per pound" is 2.2 g per kg, above both.

How accurate is a protein calculator?

It gives a target, not a measurement. The ranges come from guidelines and trials on groups of people, and your own need may sit a little higher or lower. Treat the number as one to land near most days, not to hit to the gram.

Is that much protein safe?

For healthy kidneys, the trials found no harm. In a 2018 analysis of 28 studies with 1,358 adults, kidney function changed no differently on higher-protein diets than on lower or normal ones. If you have kidney disease, ask your doctor or a registered dietitian first: PROT-AGE notes that older adults with severe kidney disease may need to limit protein.

The calculator is for adults. Under 18, pregnant, breastfeeding or taking a GLP-1 weight-loss medicine? Ask the doctor or midwife who looks after you.

General information, not medical advice. If you have a health condition, are pregnant or take medication, check with your doctor or a registered dietitian before you change how you eat.