Weight loss comes down to one equation: eat fewer calories than you burn. A deficit of 500 calories per day produces roughly 1 pound of fat loss per week, since a pound of body fat contains about 3,500 calories. But the math gets personal — your Total Daily Energy Expenditure depends on age, gender, weight, height, and activity level. A 180-pound active man might burn 2,800 calories daily while a 140-pound sedentary woman might burn 1,600. This calculator determines your specific TDEE and recommends a sustainable deficit that promotes fat loss without crashing your metabolism or sacrificing muscle mass.
Calorie Deficit Calculator
Weekly Loss Rate Comparison
Daily deficit and time to lose 30 pounds at different rates.
| Weekly Loss | Daily Deficit | Time for 30 lbs | Sustainability |
|---|---|---|---|
| 0.5 lbs/week | 250 cal/day | 60 weeks | Very sustainable |
| 1 lb/week | 500 cal/day | 30 weeks | Recommended |
| 1.5 lbs/week | 750 cal/day | 20 weeks | Moderate difficulty |
| 2 lbs/week | 1,000 cal/day | 15 weeks | Aggressive, hard to maintain |
How to Use This Calculator
- Enter your age, gender, height, and current weight
- Select your activity level honestly — most people overestimate this
- View your estimated TDEE — the calories you burn in a normal day
- Choose your deficit level: 250 cal/day for slow loss, 500 for moderate, 750 for aggressive
- See your daily calorie target and estimated weekly fat loss rate
How It Works
Weight loss comes down to calories in vs. calories out. This calculator determines the exact daily calorie intake needed to reach your goal weight at a safe, sustainable pace.
The basic rule:
- One pound of body fat equals roughly 3,500 calories
- To lose 1 lb/week, you need a 500 calorie daily deficit (3,500 ÷ 7)
- The calculator uses your TDEE minus deficit to determine daily calorie target
A moderate deficit of 500-750 calories per day is considered safe and sustainable for most people. Very aggressive deficits can lead to muscle loss, metabolic adaptation, and nutritional deficiencies.
Tips & Considerations
- Never go below 1,200 calories for women or 1,500 for men without medical supervision. Extreme deficits cause muscle loss, metabolic adaptation, and nutrient deficiencies.
- A 500-calorie deficit is the sweet spot for most people — aggressive enough to see results within 2-3 weeks, sustainable enough to maintain for months.
- Your weight will fluctuate 2-5 pounds daily from water, sodium, and food volume. Track weekly averages, not daily numbers, to see real progress.
- Protein intake becomes more important in a deficit. Aim for at least 0.8g per pound of body weight to preserve muscle mass while losing fat.
Frequently Asked Questions
How much weight can I safely lose per week?
Most health professionals recommend losing 1-2 pounds per week. Losing faster than 2 pounds per week increases the risk of muscle loss, nutritional deficiencies, and gallstones. The exception is the first week or two, when water weight loss can be higher.
What is a calorie deficit?
A calorie deficit occurs when you eat fewer calories than your body burns (your TDEE). For example, if your TDEE is 2,400 calories and you eat 1,900, you have a 500-calorie deficit. Your body makes up the difference by burning stored fat.
What is the minimum safe calorie intake?
Generally, women should not eat below 1,200 calories per day and men below 1,500 calories per day without medical supervision. Very low calorie diets can cause muscle loss, nutritional deficiencies, and metabolic slowdown.
Why does weight loss slow down over time?
As you lose weight, your body requires fewer calories to maintain itself (lower TDEE). This means your initial deficit shrinks unless you adjust. Recalculate every 10-15 pounds to stay on track. Metabolic adaptation can also play a small role.
Should I use exercise to create my deficit?
The most effective approach combines diet and exercise. Relying solely on exercise to create a deficit is difficult because most people overestimate calories burned during workouts. A combination of eating slightly less and moving more is most sustainable.
How do I know my TDEE?
Use a TDEE calculator that factors in your age, gender, height, weight, and activity level. The Mifflin-St Jeor equation is the most accurate formula. You can also estimate by tracking your weight and calorie intake over 2-3 weeks.