Calorie Deficit Calculator
How many calories should you eat to lose weight?
How a Calorie Deficit Works
Your body burns a certain number of calories per day to keep you alive and moving — this is your Total Daily Energy Expenditure (TDEE). Eat fewer calories than your TDEE and your body makes up the difference by burning stored energy (primarily fat). One pound of body fat stores approximately 3,500 calories, so a deficit of 500 calories per day produces roughly 1 pound of fat loss per week. A 250-calorie deficit produces 0.5 pounds per week. A 1,000-calorie deficit produces 2 pounds per week.
The math is straightforward but the execution is not. A 500-calorie daily deficit means eating 500 fewer calories than you burn — not 500 calories total. If your TDEE is 2,400, your deficit target is 1,900 calories. Eating 500 calories total would be a 1,900-calorie deficit, which is dangerously extreme and unsustainable. The most common mistake is confusing the deficit amount with the intake amount.
Why 1 lb/Week Is the Sweet Spot
Losing 1 pound per week requires a 500-calorie daily deficit, which is achievable without feeling constantly hungry, without losing significant muscle mass, and without the metabolic slowdown that accompanies more aggressive diets. At 2 pounds per week (1,000-calorie deficit), muscle loss increases, energy drops noticeably, and the likelihood of binge-eating from deprivation rises. Research from the University of Jyväskylä found that athletes losing 0.7% of body weight per week preserved significantly more muscle than those losing 1.4% per week — roughly the difference between 1 and 2 pounds weekly for a 185-pound person.
The exception: people with significant weight to lose (50+ pounds) can safely lose 1.5-2 pounds per week in the early stages because a higher starting body fat percentage provides a larger energy reserve. As you approach your goal weight, slowing to 0.5-1 pound per week prevents the metabolic adaptation and muscle loss that derail the final phase of weight loss.
The Minimum Safe Intake
Most nutritional guidelines set 1,200 calories for women and 1,500 for men as the minimum daily intake for adequate nutrition without medical supervision. Below these thresholds, it becomes difficult to get enough protein, vitamins, and minerals from food alone. If the calculator shows a deficit target below these floors, extend your timeline rather than going below them — slow and sustainable beats fast and dangerous every time.
How accurate is TDEE?
The Mifflin-St Jeor equation used here is accurate to within 10% for most people. Use the calculated number as a starting point, eat at your deficit for 2-3 weeks, and adjust based on actual results. If you are losing faster than target, add 100-200 calories. If slower, subtract 100-200. Your body is the final arbiter, not the formula.
Do I need to exercise to lose weight?
No. Weight loss is driven by calorie deficit, which can come entirely from eating less. Exercise increases your TDEE (letting you eat more while still in deficit), preserves muscle mass, and improves health markers — but it is not required for fat loss. The most effective approach combines a moderate calorie deficit with resistance training 2-3 times per week to preserve muscle.