Calories, TDEE, and How to Manage Your Weight
A calorie is a unit of energy. Every food you eat provides energy, and every activity you do burns it. When you consistently eat more calories than you burn, the surplus is stored as body fat and your weight increases. When you consistently eat fewer calories than you burn, your body uses stored fat for energy and your weight decreases. This fundamental principle — energy balance — underlies virtually every approach to weight management, from simple calorie counting to complex dietary plans.
BMR: Your Body's Baseline
Your Basal Metabolic Rate (BMR) is the number of calories your body needs to sustain basic functions — breathing, circulation, organ function, and temperature regulation — at complete rest. It represents about 60–75% of your total daily energy expenditure. This calculator uses the Harris-Benedict revised formula: for men, BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) − (5.677 × age); for women, BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) − (4.330 × age).
TDEE: Your Total Daily Energy Expenditure
TDEE is your BMR multiplied by an activity factor that accounts for how much you move throughout the day. Sedentary individuals (desk job, minimal exercise) multiply by 1.2. Lightly active (1–3 workouts per week) multiply by 1.375. Moderately active (3–5 workouts) multiply by 1.55. Active (6–7 workouts) multiply by 1.725. Very active (physical job or twice-daily training) multiply by 1.9. Your TDEE is the number of calories you need to eat to maintain your current weight.
Creating a Calorie Deficit for Weight Loss
One kilogram of body fat contains approximately 7,700 calories (3,500 per pound). To lose 0.5 kg per week, you need to eat approximately 500 fewer calories per day than your TDEE. To lose 1 kg per week, cut 1,000 calories per day. A deficit larger than 1,000 calories daily is generally not recommended without medical supervision, as it can cause muscle loss, nutritional deficiencies, and metabolic adaptation. Slower, sustained weight loss of 0.5 kg per week is often more effective for long-term results.
Calories for Weight Gain
To gain muscle mass, most recommendations suggest eating 250–500 calories above your TDEE combined with consistent resistance training. A surplus of 500 calories per day can lead to approximately 0.5 kg of weight gain per week. Without strength training, excess calories are more likely to be stored as fat rather than muscle. For athletes and bodybuilders, calorie cycling — eating more on training days and less on rest days — can optimize body composition.
The Limits of Calorie Counting
Calorie estimates are just that — estimates. Food labels have a permitted margin of error, and individual metabolic rates vary due to genetics, gut microbiome, hormones, and other factors. Appetite hormones like leptin and ghrelin also adapt to sustained deficits, which is why weight loss often slows after the first few weeks. Use this calculator as a starting point and adjust based on your actual results over two to four weeks. If your weight is not changing as expected, recalculate and adjust by 100–200 calories.
This calculator is for general estimates only and is not medical advice. Consult a healthcare professional before making significant changes to your diet.