Calorie Deficit Calculator
Understand how a daily calorie deficit drives fat loss and how to determine a safe deficit size based on your maintenance calorie needs.
A calorie deficit occurs when you consume fewer calories than your body expends. Over time, this cumulative energy shortfall causes your body to mobilize stored fat as an alternative fuel source — resulting in body weight reduction. The size and sustainability of your deficit determines how rapidly and safely weight loss occurs.
How It Works
Your maintenance calories (TDEE) is the energy your body needs to sustain its current weight. All deficit calculations start here. Use your BMR multiplied by your physical activity factor.
A modest deficit of 250–300 kcal/day supports gentle fat loss (~0.25 kg/week). A standard deficit of 550 kcal/day targets roughly 0.5 kg (1 lb) loss per week. A larger deficit of 1,100 kcal/day accelerates loss but increases hunger and muscle risk.
Daily intake should not fall below 1,500 kcal for men or 1,200 kcal for women, regardless of TDEE. Below these thresholds, nutritional deficiencies and metabolic adaptation become a meaningful risk.
Worked Calculation Examples
The following examples use the Mifflin-St Jeor BMR equation and standard activity multipliers — the same methodology used by the interactive calculators on this site. Figures are estimates for illustrative purposes.
Example A — 28-year-old Female, 72 kg, 168 cm, Sedentary
BMR ≈ 1,469 kcal/day. TDEE (sedentary × 1.2) ≈ 1,763 kcal/day.
Modest deficit (−275 kcal/day): Target ≈ 1,488 kcal/day → ~0.25 kg/week loss. Standard deficit (−550 kcal/day): Target ≈ 1,213 kcal/day → ~0.5 kg/week loss.
The −550 kcal target lands near the 1,200 kcal safety floor for women. Actual intake should not fall below 1,200 kcal.
Example B — 40-year-old Male, 95 kg, 182 cm, Lightly Active
BMR ≈ 1,893 kcal/day. TDEE (lightly active × 1.375) ≈ 2,602 kcal/day.
Standard deficit (−550 kcal/day): Target ≈ 2,052 kcal/day → ~0.5 kg/week. Aggressive deficit (−1,100 kcal/day): Target ≈ 1,502 kcal/day → ~1 kg/week.
Aggressive deficits are only appropriate short-term and under professional guidance.
Get Your Personalized Result
The examples above use reference figures. For results based on your exact age, sex, height, weight and activity level, use the interactive tool.
Calculate My Calorie Deficit TargetContinue Your Nutrition Planning
Calorie deficit estimates are mathematical projections. Actual fat loss varies due to metabolic adaptation, water retention, and individual differences. Do not adopt a deficit below 1,200 kcal/day (women) or 1,500 kcal/day (men) without clinical supervision. Aggressive restriction can lead to nutrient deficiencies and muscle loss.
Common Questions
What is a calorie deficit?
A calorie deficit is the state of consuming fewer calories per day than your body expends. When sustained, this energy shortfall forces the body to use stored body fat as fuel, resulting in body weight reduction over time.
How many calories should I cut to lose weight?
A deficit of approximately 550 kcal/day below your maintenance TDEE produces an estimated 0.5 kg (1 lb) of fat loss per week for most people. Smaller deficits of 250–300 kcal/day provide gentler, more sustainable loss.
Does a larger calorie deficit always mean faster weight loss?
Not reliably. Very large deficits increase muscle protein breakdown, trigger adaptive thermogenesis (metabolic slowdown), and are harder to sustain. A moderate, consistent deficit over weeks and months produces better long-term outcomes than aggressive short-term restriction.
What is a safe calorie deficit?
Most guidelines consider 250–550 kcal/day below maintenance to be a safe, sustainable deficit range for most healthy adults. This supports 0.25–0.5 kg (0.5–1 lb) loss per week without significant muscle loss or micronutrient risk.
Will I lose muscle on a calorie deficit?
Some degree of lean mass loss can occur during any calorie deficit, particularly during larger deficits. High protein intake (2.0–2.4 g/kg body weight) and regular resistance training are the two most effective strategies to minimize muscle loss while in a deficit.
Medical Disclaimer: All calorie and weight estimates on this page are mathematical projections based on population-level reference equations. They are not medical diagnoses or prescriptions. Individual results vary. Consult a qualified physician or registered dietitian before making significant changes to your diet, especially if you have a medical condition, are pregnant, or are managing a nutritional disorder.