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Calorie Deficit
Calculator

Find out exactly how many calories you need to eat to reach your goal weight, and see your customized weight loss timeline.

Usually 300 - 500 kcal

The Science of a Calorie Deficit

Weight loss fundamentally comes down to energy balance. Your body requires a certain amount of energy every day to stay alive and move around—this is your Total Daily Energy Expenditure (TDEE).

When you eat exactly your TDEE in calories, your weight stays the same. When you eat fewer calories than your TDEE, you create a calorie deficit. To make up for this missing energy, your body is forced to break down stored tissue (fat and muscle).

How Many Calories Are in a Pound of Fat?

It is widely accepted that one pound of body fat contains approximately 3,500 calories of usable energy. Therefore:

  • A deficit of 500 calories per day = 3,500 calories per week = ~1 lb of fat loss per week.
  • A deficit of 250 calories per day = 1,750 calories per week = ~0.5 lb of fat loss per week.

The Danger of a Massive Deficit (Crash Dieting)

It can be tempting to create a massive deficit (e.g., 1,000+ calories a day) to lose weight quickly. However, this is counterproductive for several reasons:

  1. Muscle Loss: Your body cannot mobilize fat fast enough to meet severe energy shortages, so it breaks down muscle tissue for fuel.
  2. Metabolic Adaptation: Severe calorie restriction signals to your body that you are starving. Your body responds by lowering your Basal Metabolic Rate (BMR), meaning you burn fewer calories at rest, making further weight loss incredibly difficult.
  3. Binge Eating: Extreme restriction disrupts hunger hormones (ghrelin and leptin), overwhelmingly increasing the psychological urge to binge.

The Sweet Spot: Aim for a deficit of 15% to 20% of your TDEE. For most people, this is between 300 and 500 calories per day.

FAQ

Calorie Deficit FAQ

A calorie deficit occurs when you consume fewer calories than your body burns in a day (your TDEE). When in a deficit, your body must burn stored energy (fat) to make up the difference, resulting in weight loss.
A safe and sustainable calorie deficit is generally 300 to 500 calories below your TDEE. This results in about 0.5 to 1 lb of fat loss per week. Deficits larger than 1,000 calories can cause muscle loss, fatigue, and metabolic adaptation.
If you aren't losing weight, you are not actually in a calorie deficit. This usually happens because you have overestimated your TDEE (often by choosing an activity level that is too high) or underestimated your calorie intake (not weighing food on a scale).