Calorie Deficit Calculator

A calorie deficit is the cornerstone of fat loss. This calculator determines how large your daily deficit should be based on your current TDEE, goal weight, and desired timeline, helping you lose weight at a safe, sustainable pace.

Advertisement
Advertisement

What Is a Calorie Deficit?

A calorie deficit occurs when you consume fewer calories than your body expends. Because your body needs energy to function, it makes up the difference by tapping into stored energy, primarily body fat. Over time, a consistent calorie deficit leads to fat loss and reduced body weight. This fundamental energy-balance principle is supported by decades of metabolic research.

The size of your deficit determines the rate of weight loss. One pound of body fat stores roughly 3,500 calories, so a daily deficit of 500 calories theoretically produces about one pound of fat loss per week. However, actual results vary due to water retention, metabolic adaptation, and changes in lean mass.

How to Calculate Your Deficit

  • Step 1: Determine your TDEE (Total Daily Energy Expenditure).
  • Step 2: Subtract your desired daily deficit (typically 300-750 calories).
  • Step 3: The result is your daily calorie target for weight loss.

Recommended Deficit Sizes

Deficit LevelDaily DeficitExpected Loss/WeekBest For
Conservative250-300 cal~0.5 lbPreserving muscle, slow and steady
Moderate500 cal~1 lbMost people, sustainable long-term
Aggressive750-1000 cal~1.5-2 lbsSignificantly overweight individuals

Limitations and Safety

Extremely large deficits (more than 1,000 calories per day) can cause muscle loss, nutrient deficiencies, hormonal disruption, and metabolic slowdown. Most health authorities recommend losing no more than 1-2 pounds per week. Women should generally not eat below 1,200 calories per day, and men below 1,500 calories, without medical supervision. If you have a medical condition, are pregnant, or are under 18, consult a healthcare provider before starting any calorie-restriction plan.

Related Calculators

BMR Calculator

Determine how many calories your body burns at complete rest with the Mifflin-St Jeor equation.

Calculate now

TDEE Calculator

Estimate your Total Daily Energy Expenditure based on BMR and activity level.

Calculate now

Macronutrient Calculator

Split your daily calories into optimal protein, carb, and fat targets for your goal.

Calculate now

Frequently Asked Questions

How big should my calorie deficit be?
A moderate deficit of about 500 calories per day is suitable for most people and produces roughly one pound of fat loss per week. If you have a lot of weight to lose, a slightly larger deficit may be safe. If you are already lean, a smaller deficit of 250-300 calories helps preserve muscle mass.
Will a calorie deficit make me lose muscle?
Some muscle loss is common during a deficit, but you can minimize it by keeping protein intake high (1.6-2.2 g/kg of body weight), performing resistance training 3-4 times per week, and keeping your deficit moderate. These strategies signal your body to preserve lean tissue while prioritizing fat for energy.
How long should I stay in a calorie deficit?
Most experts recommend dieting phases of 8-16 weeks followed by a maintenance phase of equal length. Prolonged deficits can lead to metabolic adaptation and diet fatigue. Taking periodic diet breaks at maintenance calories can improve adherence and metabolic health.
Why is my weight loss stalling despite a deficit?
Plateaus are common and can result from metabolic adaptation, water retention, inaccurate calorie tracking, or unconscious increases in food intake. Reassess your TDEE with your current weight, verify portion sizes, and consider a brief diet break. If the plateau persists for more than 3 weeks, consult a dietitian.
Advertisement