Find out exactly how many calories you need per day to lose weight, maintain, or build muscle — plus your macro targets.
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Basal Metabolic Rate is what you burn lying still. It's the floor of your energy needs — even a coma patient burns this many calories.
Eat at your TDEE and your weight stays the same. Go below it to lose, above it to gain. Simple energy balance.
Calories come from protein, carbs, and fat. Protein targets are higher during a cut to preserve muscle. Fat stays above a minimum for hormone health.
Total daily energy expenditure has four parts. Basal metabolic rate — energy used at complete rest for breathing, circulation, brain function and cell maintenance — is the largest, usually 60 to 70 percent of the total. The thermic effect of food, the energy spent digesting and absorbing what you eat, accounts for roughly 10 percent, and is higher for protein than for fat or carbohydrate.
Deliberate exercise is often the smallest component, typically 5 to 15 percent for people who are not athletes — which surprises those who assume a gym session dominates the day's expenditure. Non-exercise activity thermogenesis, covering walking, fidgeting, standing and everything incidental, is the most variable, and can differ by hundreds of calories a day between people of similar size.
BMR is estimated from equations. The Mifflin-St Jeor equation is generally the most accurate for the general population, superseding the older Harris-Benedict; the Katch-McArdle equation uses lean body mass instead of total weight and is better where body composition is known, since muscle is more metabolically active than fat.
Prediction equations carry meaningful error. Even the better ones are typically within about 10 percent for most people, which on a 2,500 calorie requirement is a 250 calorie band — larger than many deliberate deficits. Individual variation in metabolic rate at the same height, weight, age and sex can be 20 percent or more, driven by genetics, thyroid function, body composition and past dieting history.
Activity multipliers add further imprecision, and they are where most overestimation happens. The categories are broad and self-assessment is systematically generous — people consistently overestimate both how much they move and how hard they work. Choosing a lower activity level than feels accurate usually produces a closer figure.
Expenditure is also not fixed. It adapts: sustained calorie restriction reduces both BMR and, more substantially, spontaneous movement, which is a large part of why weight loss slows over time. This is metabolic adaptation, and it means a figure calculated at the start of a diet does not stay valid.
Treat it as a starting hypothesis rather than a prescription. Eat at the estimate for two to three weeks while tracking weight and intake consistently, then adjust based on what actually happened — the observed result is real data about your metabolism, which no equation can provide.
Weight fluctuates by a kilogram or more day to day from water, glycogen, sodium and digestive contents, so a weekly average is far more informative than any single morning's reading. A trend across two or three weeks is what tells you whether the intake is right.
For weight loss, a deficit of roughly 10 to 20 percent below maintenance is generally sustainable and preserves lean mass better than an aggressive one; very large deficits increase muscle loss and adaptation. Adequate protein and resistance training both help retain lean mass. This calculator produces an estimate and is not medical or nutritional advice. Anyone with a medical condition, a history of disordered eating, who is pregnant or breastfeeding, or who is considering a substantial change in diet should speak to a doctor or a registered dietitian first — and calorie targets are not appropriate for everyone.
This uses the Mifflin-St Jeor equation (the most validated formula for the general population) and standard TDEE activity multipliers. Real-world results vary ±10–15% because activity levels are self-reported and metabolisms differ. Use the result as a starting point, track for 2–3 weeks, and adjust by 100–150 kcal if you're not seeing the expected change.
Different calculators use different BMR formulas (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle) and different activity multipliers. Mifflin-St Jeor is recommended by the Academy of Nutrition and Dietetics as the most accurate for most adults.
Hit your protein target first — it's the most important for muscle retention and satiety. Fill the rest of your calories with carbs and fat in whatever ratio you prefer. You don't need to hit macros exactly every day — weekly averages matter more.
Losses faster than 1 kg/week typically include significant muscle loss. Most nutrition guidelines recommend a maximum deficit of 500–750 kcal/day. Larger deficits are sometimes used medically under supervision.
Usually within about 10 percent, which on 2,500 calories is a 250 calorie band. Individual variation at the same height, weight and age can exceed 20 percent. Use it as a starting point and adjust based on two to three weeks of actual results.
Expenditure adapts — sustained restriction lowers basal rate and, more significantly, spontaneous daily movement. A figure calculated at the start of a diet does not stay accurate. Recalculate at your current weight and consider a diet break.