Calorie Deficit Calculator — Daily Target for Weight Loss

1 lb fat ≈ 3,500 calories

Daily deficit = Goal (lbs/week) × 500
Calorie target = TDEE − Daily deficit

Safe minimums:
1,200 cal/day for women
1,500 cal/day for men

The 500 calorie per pound relationship is a useful approximation. Actual results vary due to metabolic adaptation, water retention, and the ratio of fat to muscle lost.

Daily target (TDEE A1, deficit B1)

=A1-B1

Calorie Deficit for Weight Loss ExplainedSearch YouTube tutorials →

How a Calorie Deficit Drives Weight Loss

Weight loss requires a sustained caloric deficit — burning more calories than you consume. When your body needs more energy than food provides, it draws on stored energy (primarily fat) to make up the difference. One pound of body fat stores approximately 3,500 calories, which is why a 500 calorie/day deficit theoretically produces about one pound of loss per week.

In practice, early weight loss is faster than the math suggests because glycogen (stored carbohydrate) is also depleted. Each gram of glycogen is stored with about 3 grams of water, so reducing carbohydrate intake or calories causes rapid initial water weight loss. As glycogen stores stabilize, loss slows to actual fat loss rate.

Metabolic adaptation is the other complicating factor. The body responds to sustained caloric restriction by reducing its metabolic rate — burning fewer calories in response to less food. This is the body's evolutionary response to perceived famine. The adaptation means the same deficit produces less loss over time, which is why weight loss often plateaus despite consistent effort.

Sustainable Deficit Sizes

A 500 calorie/day deficit (targeting 1 lb/week) is the sweet spot recommended by most nutrition professionals. It produces meaningful, visible progress without the downsides of aggressive restriction: muscle loss, hormonal disruption, intense hunger, and the psychological fatigue of severe dieting.

Deficits larger than 750-1,000 calories/day increase the risk of muscle loss (the body cannibalizes protein for energy when severely depleted), nutritional deficiencies (hard to meet micronutrient needs on very low calories), and metabolic adaptation. The generally accepted minimums — 1,200 calories for women and 1,500 for men — exist because below these thresholds it becomes difficult to eat a nutritionally complete diet.

Frequently Asked Questions

The 3,500-calorie-per-pound rule is an approximation. Actual composition of weight lost varies (fat vs muscle vs water vs glycogen). Metabolic adaptation reduces TDEE over time. Water retention from inflammation, hormonal cycles, and sodium intake creates day-to-day fluctuations. Track weekly averages rather than daily weigh-ins for a more accurate picture.

A combination works best and is more sustainable. Diet changes are more calorie-efficient — cutting 500 calories takes less effort than burning 500 calories through exercise. But exercise preserves muscle mass during a deficit, partially mitigates metabolic adaptation, and improves long-term maintenance. The psychological benefits of exercise also support adherence.

The body's reduction in energy expenditure in response to sustained caloric restriction, beyond what weight loss alone would predict. It can reduce TDEE by 10-15% or more. Strategies to minimize it: avoid very large deficits, maintain high protein intake, incorporate resistance training, and take periodic "diet breaks" (returning to maintenance calories for 1-2 weeks).

Below 1,200 calories for women and 1,500 for men without medical supervision. Very low calorie diets (under 800 calories) should only be undertaken with physician oversight and typically involve medical meal replacement products designed to meet nutritional needs at extremely low calorie levels. Unsupervised crash dieting can cause serious health problems including gallstones, electrolyte imbalances, and cardiac issues.