Last updated: May 2026
Find your ideal daily calorie target to lose weight at a safe, sustainable pace.
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Mifflin-St Jeor BMR: Male: (10×kg) + (6.25×cm) − (5×age) + 5. Female: same minus 161. Multiply by activity factor = TDEE.
The 3,500 calorie rule: 1 lb of fat ≈ 3,500 calories. A 500-calorie/day deficit = ~1 lb/week loss. This is a well-established estimate, though individual variation exists.
Safe deficit range: 250–750 calories/day for most people. Never go below 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision. Very large deficits cause muscle loss and metabolic adaptation.
⚠️ These are estimates based on population averages. Individual metabolism varies. Consult a healthcare provider or registered dietitian before starting a significant calorie restriction program.
A calorie deficit occurs when you consume fewer calories than your body burns in a given day. Your body's total daily energy expenditure (TDEE) is the sum of your basal metabolic rate, physical activity, and the thermic effect of food. When intake falls below that number, your body taps stored fat (and potentially muscle) for the remaining energy — which is how weight loss happens.
The size of your deficit determines your rate of loss and your risk of side effects. Too small a deficit means slow progress; too large a deficit risks muscle loss, fatigue, hormonal disruption, and metabolic adaptation. Most nutrition researchers and registered dietitians recommend a deficit between 300–750 calories per day for sustainable fat loss while preserving lean muscle mass.
| Deficit Per Day | Weekly Loss | Rate | Notes |
|---|---|---|---|
| 250 cal | ~0.5 lb | Slow | Very sustainable; minimal hunger; good for active people near goal weight |
| 500 cal | ~1 lb | Moderate | Most recommended starting point; balances results with muscle preservation |
| 750 cal | ~1.5 lb | Moderate-aggressive | Workable for heavier individuals; monitor energy and strength levels |
| 1,000 cal | ~2 lb | Aggressive | Generally considered the safe maximum; harder to sustain long-term |
| 1,250+ cal | >2 lb | Too aggressive | High muscle loss risk; metabolic slowdown; not recommended without medical supervision |
| Surplus 250 cal | ~+0.5 lb | Gaining (lean bulk) | Minimizes fat gain while supporting muscle growth |
| Surplus 500 cal | ~+1 lb | Gaining (fast bulk) | Faster mass gain but more fat accumulation alongside muscle |
What is a calorie deficit?
A calorie deficit means you are consuming fewer calories than your body burns each day. The gap between intake and expenditure forces your body to use stored energy — primarily body fat — to make up the difference, resulting in weight loss over time.
How big should my calorie deficit be?
For most people, a deficit of 300–500 calories per day strikes the best balance between progress and sustainability. This produces roughly 0.5–1 lb of fat loss per week without significant muscle loss, excessive hunger, or metabolic slowdown.
Does exercise count toward my deficit?
Yes. Exercise increases your TDEE, which effectively widens your deficit if you don't eat back the calories burned. However, many tools (including this calculator) already factor activity level into TDEE, so avoid double-counting exercise if you selected an active multiplier.
Can you eat too little on a deficit?
Absolutely. Eating below roughly 1,200 kcal/day for women or 1,500 kcal/day for men can trigger muscle catabolism, nutrient deficiencies, hormonal disruption, and metabolic adaptation — where your body burns fewer calories at rest to compensate for low intake.
What is TDEE and why does it matter?
TDEE stands for Total Daily Energy Expenditure — the total number of calories your body burns each day including basal metabolic rate, physical activity, and the thermic effect of digesting food. Your deficit is always measured against TDEE, so accurately estimating it is the foundation of any effective weight-loss plan.