How to Calculate a Calorie Deficit for Weight Loss

What Is a Calorie Deficit?

A calorie deficit occurs when you consume fewer calories than your body burns. Since 3,500 calories roughly equals one pound of fat, a deficit of 500 calories per day produces approximately one pound of weight loss per week. This is the fundamental mechanism behind all weight loss approaches.

Step 1: Calculate Your TDEE

Your Total Daily Energy Expenditure (TDEE) is the number of calories you burn in a day accounting for activity. Start with your Basal Metabolic Rate (BMR) — calories burned at rest — then multiply by an activity factor: sedentary (1.2), lightly active (1.375), moderately active (1.55), very active (1.725).

Step 2: Choose Your Deficit Size

Mild deficit (250–300 cal/day): ~0.5 lb/week. Easiest to sustain, minimal muscle loss risk.
Moderate deficit (500 cal/day): ~1 lb/week. The standard recommended rate for most people.
Aggressive deficit (750–1,000 cal/day): ~1.5–2 lb/week. May cause muscle loss, fatigue, and hunger.

Step 3: Set Your Calorie Target

Subtract your desired deficit from your TDEE. For example: TDEE of 2,400 minus a 500-calorie deficit = 1,900 calories per day. Most dietitians recommend not going below 1,200 calories (women) or 1,500 calories (men) without medical supervision.

Tracking and Adjusting Over Time

Apps like MyFitnessPal make calorie tracking feasible. Track for 2–4 weeks before drawing conclusions — day-to-day water weight fluctuations can mask fat loss trends. If weight loss stalls for 2+ weeks, recalculate TDEE based on new weight and try a brief diet break before resuming.

Frequently Asked Questions

How big should my calorie deficit be?

A 500 calorie/day deficit targeting 1 lb/week is the most widely recommended approach. Larger deficits can work faster but increase muscle loss and are harder to sustain. For most people, 0.5–1% of body weight per week is a safe, sustainable rate.

Can I create a deficit through exercise alone?

Theoretically yes, but practically difficult. A 30-minute jog burns roughly 300 calories — you'd need considerable daily exercise to create a 500-calorie deficit. Most people find a combination of modest dietary reduction and increased activity most sustainable.