Find your TDEE (total daily energy expenditure), BMR, and macros for weight loss or muscle gain. Free calorie deficit calculator using the Mifflin-St Jeor equation — trusted by US dietitians.
A calorie calculator estimates how many calories you burn per day (your TDEE) from your age, sex, height, weight and activity level using the Mifflin-St Jeor equation. To lose weight, eat below that number; to gain, eat above it; to maintain, match it.
Daily calorie needs based on age, weight, height & activity
This TDEE calculator uses the Mifflin-St Jeor equation, the formula endorsed by the Academy of Nutrition and Dietetics as the most accurate for estimating calorie needs. Your BMR (basal metabolic rate) is the number of calories your body burns at complete rest — just keeping your heart beating, lungs breathing, and organs functioning. Multiply your BMR by an activity factor and you get your TDEE: the total calories you burn each day. Creating a calorie deficit below your TDEE causes weight loss; eating above it causes weight gain. A deficit of 500 calories per day produces roughly one pound of fat loss per week — a sustainable rate most US nutrition guidelines consider safe.
For a 28-year-old moderately active male, 5'9", 175 lbs, the TDEE is roughly 2,650 calories. To lose 1 lb per week, he'd eat 2,150 calories. To gain muscle, he'd eat 2,900–3,100. The macro ratios matter too: most fitness-focused plans allocate 25%–35% of calories to protein, 40%–50% to carbohydrates, and 20%–30% to fat. Higher protein (40%+) is common on low-carb and keto diets, which shift carb calories to fat. This weight loss calculator gives you the starting numbers; adjusting based on real-world results over two to three weeks refines the estimate for your specific metabolism.
A 500-calorie daily deficit creates a 3,500-calorie weekly deficit — roughly 1 lb of fat. Aggressive deficits above 1,000 calories/day often cause muscle loss and metabolic adaptation. Slow and steady works better long-term.
A sedentary desk worker burns 20%–30% fewer calories than the same person doing moderate exercise 5 days a week. Overestimating activity level is the most common reason people eat "maintenance" and still gain weight.
US Dietary Guidelines recommend 0.8g protein per kg bodyweight for general health. For fat loss with muscle preservation, most sports dietitians recommend 1.6–2.2g per kg. For a 175 lb person, that's 125–175g protein daily.
After 4–6 weeks of a calorie deficit, your body adapts by lowering TDEE by 5%–15%. This is why weight loss often slows over time. Recalculating TDEE every 10–15 lbs of weight lost keeps your deficit accurate.
A daily calorie target is built in two stages: estimate maintenance from basal metabolic rate and activity, then apply a deficit or surplus for the goal. The deficit size is the decision that matters. A 20% deficit is aggressive enough to produce visible progress and moderate enough to preserve lean mass and adherence; deficits beyond 25% increase muscle loss without proportionally accelerating fat loss, and they are far harder to sustain. The other constraint is a floor — dropping below basal metabolic rate for extended periods is counterproductive and is where most crash diets fail.
BMR (Mifflin-St Jeor, men) = (10 × kg) + (6.25 × cm) − (5 × age) + 5Maintenance = BMR × activity factorCutting = Maintenance × 0.80 · Bulking = Maintenance × 1.10Weekly change (lb) = (daily deficit × 7) ÷ 3,500where:
Assumptions: An estimate for healthy adults. Recalculate after every 5–10 lb of change, because maintenance falls as body mass falls. Not appropriate during pregnancy, for children, or where an eating disorder is a concern.
A 35-year-old man, 82 kg and 178 cm, training three times a week at a desk job.
Result1,939 calories a day — about 1 lb a week
Selecting "moderate" (1.55) instead would put maintenance at 2,732 and the target at 2,186 — which is close to true maintenance, so nothing would happen. Under-stating activity is the safer error, because a stalled result at a low intake is easier to diagnose than an invisible surplus.