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.
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.