Protein Calculator — Daily Needs
Calculate daily protein needs by weight, activity and goals. ISSN-backed formula with Boer lean-mass estimation and meal distribution. Free.
What to calculate next?
CalcVita. (2026). Protein Calculator — Daily Needs. CalcVita. Retrieved October 24, 2026, from https://calcvita.com/en/calculators/protein
Quick guide to the protein calculator
This protein calculator uses ISSN-backed formulas to estimate your daily protein needs. It considers your weight, height, age, sex, activity level, and goal to deliver a personalized recommendation. Lean body mass is estimated via the Boer equation (1984) — a widely used prediction equation — unless you provide your body fat percentage directly.
How the calculation works
The engine starts with a base protein requirement per kilogram (0.8 g/kg for sedentary up to 2.0 g/kg for competitive athletes), then applies goal-specific adjustments: +0.3 g/kg for muscle gain or recomposition, +0.4 g/kg for weight loss (to preserve lean tissue during a caloric deficit). An age factor adds 0.2-0.3 g/kg for adults over 50 to counteract age-related muscle loss. The total is capped at 2.4 g/kg: in a 2018 meta-analysis (Morton et al.), protein beyond about 1.6 g/kg/day brought no further gains in fat-free mass with resistance training.
Understanding each field
Weight (kg)
Your current body weight in kilograms. This is the primary variable in protein calculations.
Height (cm)
Used in the Boer lean body mass formula when body fat percentage is not provided.
Age (years)
Adults over 50 receive a higher protein recommendation due to increased anabolic resistance and sarcopenia risk.
Biological sex
Affects lean body mass estimation: the Boer formula uses different coefficients for males and females.
Body fat percentage (optional)
If known, provides a more accurate lean body mass calculation. Typical ranges: 10-20% for men, 20-30% for women.
Activity level
Ranges from sedentary (0.8 g/kg base) to competitive athlete (2.0 g/kg base). Choose the level that best reflects your regular training volume and intensity.
Primary goal
Muscle gain and recomposition add +0.3 g/kg, weight loss adds +0.4 g/kg. Maintaining bodyweight uses the base recommendation.
Interpreting your results
The calculator provides a recommended daily intake (grams), a range (minimum-maximum), and a tier classification: Minimum (below 1.2 g/kg — adequate for sedentary lifestyles), Recommended (1.2-1.8 g/kg — optimal for most active individuals), or Athlete (above 1.8 g/kg — for high-volume training or competitive sport). The meal distribution suggests how to spread protein across the day for optimal muscle protein synthesis.
Limitations
This calculator provides estimates based on population-level research. Individual needs may vary based on genetics, training status, health conditions, and dietary factors. It does not account for specific medical conditions (e.g., kidney disease). Always consult a registered dietitian or physician for personalized medical nutrition therapy.
Practical tips
- Spread your protein across 3-6 meals to maximize muscle protein synthesis — aim for 20-40 g per meal (ISSN, Jäger et al., 2017).
- Combine higher protein intake with resistance training for best results in muscle gain and body recomposition.
- Prioritize complete protein sources (eggs, dairy, meat, fish, soy) that provide all essential amino acids, especially leucine.
Scientific sources
- Jäger R et al. (2017) — ISSN Position Stand: Protein and Exercise. J Int Soc Sports Nutr. 14:20. PMID 28642676
- Morton RW et al. (2018) — Protein supplementation and resistance training gains in muscle mass. Br J Sports Med. 52(6):376-384. PMID 28698222
- WHO/FAO/UNU (2007) — Protein and amino acid requirements in human nutrition. Technical Report Series 935.
- Bauer J et al. (2013) — Evidence-based recommendations for optimal dietary protein intake in older people (PROT-AGE). J Am Med Dir Assoc. 14(8):542-559. PMID 23867520
- Longland TM et al. (2016) — Higher compared with lower dietary protein during an energy deficit combined with intense exercise. Am J Clin Nutr. 103(3):738-746. PMID 26817506
- Schoenfeld BJ & Aragon AA (2018) — How much protein can the body use per meal for muscle-building? JISSN. 15:10. PMID 29497353
Frequently asked questions
- How much protein do I need per day?
- The International Society of Sports Nutrition (ISSN, 2017) considers 1.4-2.0 g/kg/day sufficient for most exercising individuals. For adults in general, WHO/FAO/UNU (2007) put the requirement at about 0.8 g/kg/day of good-quality protein. Your optimal intake depends on activity level, goals and age: for people over 65, the PROT-AGE group recommends at least 1.0-1.2 g/kg/day to help maintain muscle mass and function.
- Can I eat too much protein?
- In healthy, active people, the ISSN position stand (Jäger et al., 2017) notes that published reviews find no sign of kidney or liver harm from higher protein intakes, and cites a study in which resistance-trained participants ate up to 3.4 g/kg/day for eight weeks with no change in the usual kidney or liver blood markers. People with pre-existing kidney disease should consult a physician before increasing their intake.
- How is the protein requirement calculated?
- Our calculator starts from a base value per kg set by your activity level (from 0.8 g/kg if sedentary to 2.0 g/kg for competitive athletes), then adds an adjustment for your goal (+0.3 g/kg for muscle gain or recomposition, +0.4 g/kg for weight loss) and for age (+0.2 g/kg over 50, +0.3 g/kg over 65), up to a maximum of 2.4 g/kg. That figure is multiplied by your total body weight. Lean body mass — estimated with the Boer formula (1984) when you do not enter your body fat percentage — is shown for reference.
- Why do I need more protein when losing weight?
- During a caloric deficit, a higher protein intake helps preserve lean mass while losing fat; the ISSN (2017) notes that resistance-trained people may need 2.3-3.1 g/kg/day during hypocaloric periods. In a 2016 trial by Longland et al. (American Journal of Clinical Nutrition), young men eating 2.4 g/kg/day during a deficit combined with intense exercise gained more lean mass and lost more fat than a group eating 1.2 g/kg/day. Protein also increases satiety, helping control appetite.
- When is the best time to eat protein?
- Research supports spreading protein evenly through the day. The ISSN recommends about 0.25 g/kg — or 20-40 g — of high-quality protein per serving every 3-4 hours, and Schoenfeld & Aragon (2018) suggest about 0.4 g/kg per meal across at least four meals. Eating protein before or after training both work; total daily intake matters more than precise timing.
- What are the best sources of protein?
- Complete proteins containing all essential amino acids include: lean meats, poultry, fish, eggs, dairy, soy, and quinoa. Animal sources typically have higher bioavailability and leucine content, which is key for MPS. Plant-based diets can meet protein needs by combining legumes, grains, nuts, and seeds. The DIAAS (Digestible Indispensable Amino Acid Score) ranks eggs, dairy, and meat highest for protein quality.
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