A calorie deficit occurs when you consume fewer calories than your body burns (Total Daily Energy Expenditure, or TDEE). This forces your body to use stored body fat for energy, resulting in weight loss. A safe and sustainable deficit is typically 500 calories per day, leading to about 0.5 kg (1 lb) of weight loss per week.

First, calculate your Basal Metabolic Rate (BMR) using a formula like Mifflin-St Jeor. Then, multiply your BMR by an activity factor to find your TDEE. Finally, subtract your desired daily deficit (e.g., 500 kcal) from your TDEE to get your target daily calories. This calculator does all of this automatically.

BMR (Basal Metabolic Rate) is the number of calories your body needs to perform basic life-sustaining functions like breathing and circulation at complete rest. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor, representing the total calories you burn in a day including exercise and daily movement.

Health organizations generally recommend losing 0.5 to 1.0 kg (1 to 2 lbs) per week. This equates to a daily calorie deficit of 550 to 1100 calories. Losing weight faster than this can increase the risk of muscle loss, nutritional deficiencies, and gallstones, and is often unsustainable long-term.

The Mifflin-St Jeor equation is considered the most accurate formula for calculating BMR for the general population. For men, it is: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5. For women, it is the same but minus 161 instead of plus 5.

Generally, no. Your BMR represents the calories your body needs just to keep your organs functioning. Eating below your BMR for extended periods can slow down your metabolism, cause muscle loss, and lead to fatigue and hormonal imbalances. It is usually recommended to keep your calorie intake at or above your BMR.

While calories dictate weight loss, macronutrients (protein, carbs, and fats) dictate what kind of weight you lose and how you feel. In a deficit, a high protein intake (1.6-2.2g per kg of body weight) is crucial to preserve muscle mass. Fats should be kept at a minimum (about 20-25% of calories) for hormonal health, with the remaining calories coming from carbohydrates for energy.

If you are not losing weight, you may be underestimating your calorie intake (e.g., forgetting cooking oils or snacks), overestimating your activity level, or your TDEE has decreased as you lose weight. It is also normal for weight loss to stall due to water retention. Re-calculate your TDEE with your new weight and ensure you are tracking accurately.