Protein Requirement CalculatorHow Much Protein Do I Need Per Day?

Worked example (the default)

• Man, 75 kg, 175 cm → BMI 24.5, so actual weight is used
• Build muscle: 1.6–2.2 g/kg × 75 = 120–165 g a day
• Middle of the range ≈ 143 g; over 4 meals ≈ 36 g per meal
• RDA floor for comparison: 0.8 × 75 = 60 g

Why adjusted weight for BMI 30+

Protein needs track lean tissue more closely than fat. For a 120 kg person, multiplying actual weight by 1.6 gives 192 g, which overestimates what most people need. Dietitians commonly use adjusted body weight in obesity instead. For a 120 kg, 170 cm man that gives about 92 kg, or about 148 g at 1.6 g/kg. You can switch to actual weight in the calculator if your clinician prefers it.

Don’t back-load dinner

Many people eat 10 g at breakfast and 60 g at dinner. Moving 20 g to breakfast — eggs, Greek yogurt, milk or a shake — is the simplest upgrade.

Older adults need more per meal

Ageing muscle responds less to small doses (“anabolic resistance”). Aim for 25–40 g per meal rather than a large single serving.

Before bed can help

A slow-digesting protein such as casein or cottage cheese before sleep supports overnight muscle repair in people who train.

On tirzepatide or semaglutide

GLP-1 medicines cut appetite so much that protein intake often falls, and part of the weight lost is muscle. A 2025 joint advisory from four obesity and nutrition societies listed adequate protein plus strength training as a core priority. Plan protein first at each meal, and use the tirzepatide or semaglutide calculators to check your injection math.

Healthy ageing and sarcopenia

From about age 50, muscle mass declines each year, and inactivity speeds it up. PROT-AGE recommends 1.0–1.2 g/kg for healthy adults over 65, at least 1.2 g/kg for those who exercise, and 1.2–1.5 g/kg during illness — alongside resistance exercise.

Pregnancy and breastfeeding

The RDA rises to 1.1 g/kg in the second half of pregnancy and 1.3 g/kg while breastfeeding — roughly 25 g a day more than before. Tracer studies suggest needs may be higher late in pregnancy. Your midwife or doctor can tailor this.

High-protein diets and your kidneys

In healthy adults, the evidence is reassuring. A 2018 meta-analysis by Devries and colleagues found that higher-protein diets did not change kidney function (GFR) compared with normal or lower-protein diets. Intakes up to about 2.0–2.2 g/kg are well studied. Above about 2.5–3.0 g/kg, long-term data are limited, and protein is crowding out other foods. Drink enough water, especially on a high-protein diet.

Animal vs plant protein

Animal proteins, soy and dairy score highly on protein-quality scales such as DIAAS because they contain all essential amino acids in good amounts. Most other plant proteins are lower in at least one amino acid — typically lysine in grains or methionine in legumes. The fix is simple: combine sources across the day (lentils with rice, hummus with bread) and aim toward the top of your range if you’re fully plant-based.

Protein powders: a pharmacist’s checklist

• Food first; powders are a convenience, not a requirement.
• Choose third-party-tested products (for example NSF Certified for Sport or Informed Sport), especially if you’re drug-tested.
• Check the label for grams of protein per scoop — it varies widely between brands.
• Whey is fast-digesting, casein slow, and pea or soy suit plant-based diets.

Common protein mistakes

• Treating the RDA as the target instead of the minimum.
• Using total body weight in obesity, which inflates the number.
• Eating most protein at dinner.
• Counting a whole food’s weight as protein — 100 g of chicken has about 31 g of protein, not 100 g.
• Ignoring protein while appetite is suppressed on GLP-1 medicines.