How does a nutrition calculator estimate daily calorie needs?
A nutrition calculator first estimates your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor equation — the most validated formula for general populations: BMR (men) = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; BMR (women) = 10 × weight + 6.25 × height − 5 × age − 161. It then multiplies BMR by an activity factor to get Total Daily Energy Expenditure (TDEE): Sedentary ×1.2, Lightly active ×1.375, Moderately active ×1.55, Very active ×1.725, Extra active ×1.9. Your calorie target is then adjusted for your goal: −20% for weight loss, +10–15% for muscle gain, or TDEE for maintenance.
How much protein do I need per day?
Protein needs depend on body weight and goal. Current evidence-based guidelines: Sedentary adults — 0.8 g/kg body weight (the minimum RDA). Recreational exercisers — 1.2–1.6 g/kg. Strength/hypertrophy training — 1.6–2.2 g/kg (the effective ceiling for muscle protein synthesis according to Morton et al. 2018 meta-analysis of 49 studies). Fat loss with high exercise — up to 2.4–3.1 g/kg to preserve lean mass. Example: an 80 kg person actively training for muscle gain needs 128–176 g protein/day. Spread across 4–5 meals of 30–40 g each maximises muscle protein synthesis.
What is the ideal carbohydrate and fat split for daily nutrition?
General healthy adult split (% of total calories): Carbohydrates 45–65%, Fat 20–35%, Protein 10–35% (per USDA Dietary Guidelines). Common goal-specific splits: Balanced maintenance — 50% carbs / 25% protein / 25% fat. Fat loss — 40% carbs / 30% protein / 30% fat. Muscle gain — 50% carbs / 30% protein / 20% fat. Ketogenic (metabolic goals) — 5% carbs / 20% protein / 75% fat. Prioritise carb quality (oats, sweet potato, legumes, vegetables) and fat quality (olive oil, avocado, nuts, fatty fish) over simple percentages.
How much fibre and water should I consume daily?
Fibre: USDA recommendation is 14 g per 1,000 kcal consumed. Typical targets are 25–28 g/day for women and 31–34 g/day for men. High-fibre diets are associated with lower risk of cardiovascular disease, type 2 diabetes, and colorectal cancer, and improve satiety and gut microbiome diversity. Water: European Food Safety Authority (EFSA) recommends 2.0 L/day for women and 2.5 L/day for men from all sources (food contributes ~20%). Add 400–600 mL per hour of moderate exercise. In hot climates or during intense training, total needs can reach 3–4 L/day. Urine colour is a simple hydration indicator — pale yellow is ideal.
What are micronutrient targets I should track alongside macros?
Key micronutrients to monitor alongside macros: Vitamin D — 600–800 IU/day (many people are deficient, especially with limited sun exposure). Iron — 8 mg/day (men), 18 mg/day (women 19–50), 27 mg/day (pregnant). Calcium — 1,000 mg/day (adults); 1,200 mg/day (women 51+, men 71+). Omega-3 fatty acids — 1.1–1.6 g/day ALA; aim for 2 servings fatty fish/week for EPA+DHA. Vitamin B12 — 2.4 µg/day (critical for vegans/vegetarians). Zinc — 8 mg/day (women), 11 mg/day (men). A varied whole-food diet rich in vegetables, legumes, whole grains, and lean proteins covers most micronutrient needs without supplementation.