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Calorie Deficit Calculator

A calorie deficit is the foundation of weight loss — you need to consume fewer calories than your body burns. This calculator estimates your Total Daily Energy Expenditure (TDEE), then subtracts your chosen deficit to give you a daily calorie target. It also projects how quickly you can expect to lose weight and warns you if your intake drops too low.

Quick Answer

A moderate deficit of 500 calories per day leads to roughly 1 lb (0.45 kg) of weight loss per week. Your TDEE minus your deficit equals your daily calorie target.

These results are estimates based on general formulas and are not a substitute for professional medical advice. Consult a healthcare provider before making health decisions.

Enter your details above to calculate your calorie deficit.

How the Formula Works

  1. Calculate your TDEE using the Mifflin-St Jeor equation and an activity multiplier.

    TDEE = BMR × Activity Multiplier

  2. Choose a deficit level or enter a custom deficit amount.

    Mild = 250 cal/day | Moderate = 500 cal/day | Aggressive = 750 cal/day | Extreme = 1,000 cal/day

  3. Subtract the deficit from your TDEE to get your daily calorie target.

    Daily Calories = TDEE − Deficit

  4. Estimate weekly weight loss using the 3,500-calorie rule.

    Weekly Loss (lbs) = (Deficit × 7) / 3,500

  5. If you entered a goal weight, divide total weight to lose by weekly loss rate to estimate time to goal.

Methodology & Sources

Reviewed and updated April 4, 2026 · Prepared by GetHealthyCalculators Editorial Team

This calculator pairs the Mifflin-St Jeor BMR equation with standard activity multipliers to estimate TDEE, then applies a linear deficit model. The 3,500-calorie-per-pound rule provides a simplified projection — actual results vary with metabolic adaptation, body composition, and adherence.

References

  • A new predictive equation for resting energy expenditure in healthy individuals · American Journal of Clinical Nutrition
  • Optimal Diet Strategies for Weight Loss and Weight Loss Maintenance · Journal of Obesity & Metabolic Syndrome
  • Calorie restriction and energy balance · American Journal of Clinical Nutrition

Limitations

  • The 3,500-calorie-per-pound rule is a simplification — actual weight loss is non-linear and varies with metabolic adaptation.
  • TDEE estimates have a margin of error of roughly 10%, so your actual calorie needs may differ.
  • This calculator does not account for changes in metabolism, body composition, or hormonal factors over time.
  • Extreme deficits can lead to muscle loss, nutrient deficiencies, fatigue, and metabolic slowdown.
  • Always consult a healthcare provider before starting a very low-calorie diet (below 1,200–1,500 cal/day).

Frequently Asked Questions

What is a calorie deficit?
A calorie deficit means you consume fewer calories than your body burns (your TDEE). This forces your body to use stored energy — primarily body fat — to make up the difference, leading to weight loss over time.
How big of a calorie deficit is safe?
Most health professionals recommend a deficit of 500 calories per day (about 1 lb loss per week) as a sustainable target. Deficits larger than 1,000 calories per day are generally not recommended without medical supervision.
Will a calorie deficit cause muscle loss?
Some muscle loss is common during a deficit, but you can minimize it by eating adequate protein (0.7–1 g per pound of body weight), performing resistance training, and keeping your deficit moderate rather than extreme.
Why is there a minimum calorie warning?
Eating below 1,200 calories (women) or 1,500 calories (men) per day can make it very difficult to meet essential nutrient needs and may slow your metabolism. If your deficit brings you below this threshold, the calculator warns you to consult a healthcare provider.
How accurate is the time-to-goal estimate?
The time-to-goal projection assumes a constant rate of weight loss, which rarely happens in practice. Metabolic adaptation, water weight fluctuations, and lifestyle changes all affect the timeline. Use it as a rough guide, not an exact schedule.
Should I eat back exercise calories?
Your TDEE already factors in your typical activity level. If you do additional exercise beyond your selected activity level, you may want to eat back some of those calories, but most people overestimate calories burned during exercise. A conservative approach is to eat back roughly half.

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