Calorie Deficit Calculator
Calculates the daily calorie target you need to hit your weight loss goal within a chosen timeframe, given your current TDEE. Use it to translate a pounds-to-lose goal and a deadline into a concrete daily eating target.
About this calculator
Losing one pound of body fat requires burning approximately 3,500 more calories than you consume. To lose a specific amount of weight over a set number of weeks, you need to create a precise average daily deficit. The formula used here is: Daily calorie target = TDEE − ((currentWeight − targetWeight) × 3,500) ÷ (timeframe × 7). Breaking this down: (currentWeight − targetWeight) × 3,500 gives the total caloric deficit required, and dividing by (timeframe × 7) spreads that deficit evenly across all days. Subtracting from your TDEE (Total Daily Energy Expenditure — the calories your body burns at your current activity level) yields your daily food intake target. If the resulting number falls below roughly 1,200 calories for women or 1,500 for men, the timeline should be extended to protect metabolic health.
How to use
Suppose you weigh 200 lbs, want to reach 180 lbs in 10 weeks, and your TDEE is 2,500 calories/day. Step 1 — total deficit needed: (200 − 180) × 3,500 = 20 × 3,500 = 70,000 calories. Step 2 — spread over the timeframe: 70,000 ÷ (10 × 7) = 70,000 ÷ 70 = 1,000 calories/day deficit. Step 3 — daily eating target: 2,500 − 1,000 = 1,500 calories/day. Eating 1,500 calories per day for 10 weeks should produce the target 20-lb loss, assuming TDEE stays constant.
Frequently asked questions
How many calories do I need to cut per day to lose weight?
The classic estimate is that a 500-calorie daily deficit produces roughly 1 lb of fat loss per week, based on the 3,500-calorie-per-pound rule. However, the precise number depends entirely on how much weight you want to lose and how quickly — this calculator solves for your specific situation rather than applying a generic cut. Larger or faster goals require deeper deficits, while modest or long-term goals need only a small daily reduction. Most practitioners recommend keeping the deficit between 300 and 1,000 calories per day to balance progress with sustainability.
What is TDEE and how does it affect my calorie deficit calculation?
TDEE stands for Total Daily Energy Expenditure — the total number of calories your body burns in a day, including your basal metabolic rate (BMR) plus activity. It is the foundation of any calorie-based weight management plan because it defines your maintenance level: eat above it and you gain weight, below it and you lose. An inaccurate TDEE estimate will make your target off by the same margin, so using a reliable activity multiplier or, better yet, tracking your weight versus intake over 2–3 weeks to empirically measure your TDEE will give you the most accurate results.
Is the 3500 calories per pound of fat rule accurate for long-term weight loss?
The 3,500 kcal/lb rule is a reasonable approximation for short-term planning but becomes less accurate over months because it assumes a fixed composition of weight lost and a stable metabolic rate. In reality, as you lose weight your TDEE decreases (you are a lighter person moving through the day), and the ratio of fat to lean tissue lost can vary. Research using dynamic models like the NIH Body Weight Planner shows that real-world losses often slow relative to predictions beyond the first few weeks. For best results, recalculate your deficit every 4–6 weeks as your weight and activity level change.