Calorie Calculator (TDEE): How Many Calories You Need a Day
Estimate how many calories to eat per day to maintain weight (maintenance calories / TDEE), plus BMI, BMR (Mifflin-St Jeor), and a daily macronutrient split from one set of inputs, with metric and imperial units.
Estimated results
- WHO standard
- Healthy weight
- WHO Asian-Pacific risk
- Increased risk (from 23.0)
- Protein
- 138 g/day
- Carbohydrate
- 345 g/day
- Fat
- 92 g/day
These are general estimates, not medical advice.
How this calculator works
Body mass index (BMI)
BMI divides weight in kilograms by height in metres squared (kg/m²). The WHO standard adult scale runs underweight below 18.5, healthy 18.5 to 24.9, overweight 25 to 29.9, and obesity from 30. The WHO Expert Consultation (2004) also identified increased-risk action points at BMI 23.0 and 27.5 for many Asian populations, shown here as risk thresholds rather than a separate obesity scale.
Basal metabolic rate (Mifflin-St Jeor)
BMR is the energy the body uses at rest. This tool uses the Mifflin-St Jeor (1990) equation: 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years), then + 5 for males and − 161 for females. The equation is sex-binary by design, using a male or female constant rather than making any statement about identity.
Total daily energy expenditure (TDEE)
TDEE estimates how many calories the body burns in a day by multiplying BMR by an activity factor: sedentary 1.2, lightly active 1.375, moderately active 1.55, very active 1.725, extra active 1.9. The result approximates maintenance calories, the energy that holds current weight steady. These multipliers are a widely-used estimation convention rather than a single primary-source table. The underlying science is the FAO/WHO/UNU physical activity level (PAL) framework, which groups lifestyles from sedentary to vigorous.
Daily macronutrient split
The default split allocates 50% of calories to carbohydrate, 30% to fat, and 20% to protein, all within the Institute of Medicine Acceptable Macronutrient Distribution Ranges (carbohydrate 45 to 65%, fat 20 to 35%, protein 10 to 35%). Grams come from the Atwater factors: 4 kcal per gram for carbohydrate and protein, 9 for fat.
Worked example
A 30-year-old man who is 180 cm and 80 kg has a BMI of about 24.7 (healthy on the WHO scale, increased risk on the Asian-Pacific scale). His BMR is 1,780 kcal/day. At a moderately active level (× 1.55) his TDEE is about 2,759 kcal/day, which splits into roughly 345 g carbohydrate, 92 g fat, and 138 g protein per day.
Frequently asked questions
- How many calories should I eat a day?
- A reasonable starting point is the TDEE estimate, which is basal metabolic rate multiplied by an activity factor and approximates the calories needed to maintain current weight. Individual needs vary with body composition, genetics, and daily activity, so the figure is a starting point to track and adjust over a few weeks rather than an exact target.
- Is TDEE the same as maintenance calories?
- In practice, yes. Total daily energy expenditure estimates the calories the body uses across a typical day, which is the same as the calories that maintain current weight, often called maintenance calories. Because it is an estimate built on activity multipliers, it is best treated as an approximate maintenance level to refine over time.
- How many calories do I burn a day without exercising?
- Energy used at complete rest is the basal metabolic rate, which this tool estimates with the Mifflin-St Jeor equation. Day-to-day living without structured exercise is closer to the sedentary level, which multiplies BMR by about 1.2. So a sedentary day burns roughly BMR plus the light movement of normal activity, not just BMR alone.
- How many calories should I eat to lose weight?
- Weight change follows energy balance: eating below the estimated TDEE creates an energy deficit, while eating above it adds energy. A safe, sustainable rate of change is individual and depends on starting point, goals, and health, so the calculator gives the maintenance estimate as a reference rather than a personal weight-loss prescription. A clinician or dietitian can help set a sensible target.
- What is the difference between BMR and TDEE?
- Basal metabolic rate (BMR) is the energy the body uses at complete rest to keep basic functions running. Total daily energy expenditure (TDEE) is BMR multiplied by an activity factor, so it estimates the calories burned across a typical day including movement and exercise.
- How accurate is a TDEE or calorie calculator?
- The result is a general estimate, not a measurement. The activity multipliers (1.2 to 1.9) are a widely-used estimation convention rather than a single primary-source table; the underlying science is the FAO/WHO/UNU physical activity level framework. Individual energy needs vary with body composition, genetics, and daily activity, so the figure is a starting point to adjust over a few weeks.
- Why does the calculator show two BMI scales?
- The first scale is the standard WHO adult classification. The second reflects the WHO Expert Consultation (2004), which identified increased-risk action points at BMI 23.0 and 27.5 for many Asian populations, because cardiometabolic risk can rise at lower BMI values. These are framed as risk thresholds, not a separate obesity label.
- Is BMI a good measure of health?
- BMI is a screening tool, not a diagnosis. It uses only height and weight, so it does not distinguish muscle from fat or show where fat is stored. A muscular person can register a high BMI without excess fat. It is most useful at a population level and is best interpreted alongside other measures and a clinician's assessment.
- How many grams of protein, carbs, and fat should I eat?
- This tool splits estimated daily calories into 50% carbohydrate, 30% fat, and 20% protein, then converts each to grams using the Atwater factors (4 kcal per gram for carbohydrate and protein, 9 for fat). All three sit inside the Institute of Medicine AMDR ranges. Needs vary with goals and training, so the split is one balanced default rather than a personal prescription.
References
- About Adult BMI / BMI categories — Centers for Disease Control and Prevention (CDC). Accessed 2026-05-27.
- Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies (Lancet 363:157–163) — WHO Expert Consultation, The Lancet (2004). Accessed 2026-05-27.
- A new predictive equation for resting energy expenditure in healthy individuals (Mifflin-St Jeor, 1990) — Mifflin MD et al., The American Journal of Clinical Nutrition. Accessed 2026-05-27.
- Human energy requirements: Physical activity level (PAL) (y5686e) — FAO/WHO/UNU Expert Consultation (2004), FAO. Accessed 2026-05-27.
- Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (AMDR) — Institute of Medicine, Food and Nutrition Board (2002/2005). Accessed 2026-05-27.
- International Society of Sports Nutrition Position Stand: protein and exercise (1.4–2.0 g/kg/day) — Jäger R et al., Journal of the International Society of Sports Nutrition (2017). Accessed 2026-05-27.