Calorie Deficit Calculator
Find your ideal daily calorie target to lose weight safely - based on BMR, activity level, and goal.
🔥 What is a Calorie Deficit?
A calorie deficit is the state where you consume fewer calories than your body burns in a day. Your body requires energy - measured in calories - to power every bodily function: breathing, circulation, brain activity, digestion, movement, and exercise. The total amount of energy your body needs daily is called your Total Daily Energy Expenditure (TDEE).
When you consistently eat below your TDEE, your body must source the missing energy from stored reserves - primarily body fat. This is the fundamental mechanism of all fat loss. One kilogram of body fat stores approximately 7,700 calories of energy. A consistent daily deficit of 500 calories therefore depletes roughly 3,500 calories per week, translating to approximately 0.45–0.5 kg of fat loss per week.
Your TDEE is calculated from your Basal Metabolic Rate (BMR) - the calories burned at complete rest - multiplied by an activity factor. BMR is calculated using the Mifflin-St Jeor equation, which accounts for your weight, height, age, and biological sex. Activity factors range from 1.2 (sedentary, desk job) to 1.9 (very hard physical labour plus intense daily exercise).
The size of your deficit determines the rate of weight loss. A mild deficit of 250 calories/day produces slow but very sustainable loss of about 0.25 kg/week. A moderate deficit of 500 calories/day - the standard recommendation - targets 0.5 kg/week. An aggressive deficit of 750–1,000 calories/day accelerates loss to 0.75–1 kg/week but is harder to sustain, increases hunger, and risks muscle loss if protein intake is insufficient.
Importantly, your TDEE changes as you lose weight - a lighter body burns fewer calories at rest. Recalculate your targets every 4–6 weeks as you progress to ensure your deficit remains accurate and you continue losing weight at the expected rate.
📐 Calorie Deficit Formula
📖 How to Use This Calculator
Steps to Find Your Calorie Deficit Target
💡 Example Calculations
Example 1 - Male, 30 years, 85 kg, 178 cm, Moderately Active
Example 2 - Female, 28 years, 65 kg, 162 cm, Lightly Active
❓ Frequently Asked Questions
🔗 Related Calculators
What is a calorie deficit and how does it cause weight loss?
A calorie deficit occurs when you consume fewer calories than your body burns in a day (your TDEE). Since your body needs energy to function, it compensates by burning stored energy - primarily body fat. 1 kg of body fat stores approximately 7,700 calories. A consistent deficit of 500 calories/day therefore causes roughly 0.5 kg of fat loss per week.
How many calories should I eat to lose 1 kg per week?
To lose 1 kg per week, you need a daily calorie deficit of approximately 1,100 calories (7,700 ÷ 7 days). This is aggressive - most people find a 500–750 calorie deficit more sustainable, resulting in 0.45–0.65 kg/week. Start with a moderate deficit to avoid hunger, muscle loss, and metabolic adaptation.
Should I eat back calories I burn during exercise?
Partially. If you're using the TDEE method (where your activity level already accounts for exercise), you don't need to add calories back. If you're using your BMR as the baseline and adding exercise on top, then yes - account for the calories burned during that specific workout. Most fitness apps use the TDEE method, so extra eating is rarely needed.
Why did I stop losing weight even in a calorie deficit?
This is called a weight loss plateau. Common causes: your TDEE decreases as you lose weight (recalculate every 4–6 weeks), metabolic adaptation (body becomes more efficient), underestimating calories eaten, or water retention. Also, remember that weight fluctuates 1–2 kg daily due to water, food in transit, and glycogen. Track trends over 2+ weeks, not daily numbers.
Is it safe to stay in a calorie deficit for a long time?
A moderate deficit (300–500 calories below TDEE) can be maintained safely for many months. However, periodically eating at maintenance ('diet breaks' of 1–2 weeks every 6–8 weeks) can help reset metabolism, hormones, and psychological relationship with food. Avoid chronic severe restriction (>1,000 cal deficit) as it leads to muscle loss, nutrient deficiencies, and hormonal disruption.
What is a safe calorie deficit per day?
A deficit of 300-500 calories per day is generally considered safe and sustainable, producing 0.3-0.5 kg of weight loss per week. A 500-750 calorie deficit targets 0.5 kg per week. Deficits above 1,000 calories per day are not recommended without medical supervision as they can cause muscle loss, micronutrient deficiencies, fatigue, and metabolic adaptation. Adequate protein intake (1.6-2.2 g per kg body weight) helps preserve lean muscle mass during weight loss.
Why am I not losing weight despite a calorie deficit?
Several factors can stall weight loss: (1) Inaccurate calorie counting - food scales are more accurate than visual estimates; restaurant meals often contain 30-50% more calories than listed. (2) Metabolic adaptation - the body reduces BMR during prolonged restriction. (3) Water retention from stress, high sodium, or hormonal changes causing temporary weight fluctuations. (4) Muscle gain offsetting fat loss when starting exercise. Track trends over 3-4 weeks rather than daily.
How do I avoid muscle loss while in a calorie deficit?
Three key strategies: (1) Keep protein high - 1.6-2.2 g per kg of body weight per day preserves muscle mass during a deficit. (2) Maintain resistance training - strength training signals the body to preserve muscle even when calories are limited. (3) Limit the deficit to 500-750 kcal/day; aggressive deficits (1,500+ kcal) accelerate muscle loss regardless of protein intake.