Calorie Deficit Calculator

A calorie deficit occurs when average energy intake is lower than average energy expenditure. The body then draws on stored energy, and body mass generally trends downward over time. This calculator first estimates basal metabolic rate with the Mifflin-St Jeor equation. It then applies an activity multiplier to estimate total daily energy expenditure, often called maintenance calories or TDEE. The selected weekly loss rate is converted to an energy deficit using the common approximation that one kilogram of body tissue represents about 7,700 kilocalories. A goal of 0.5 kilograms per week therefore corresponds to approximately 550 calories per day. This conversion is useful for planning, but human weight change is not perfectly linear. Fat, lean tissue, glycogen, food volume, and water all contribute to changes on the scale. A slower rate is often easier to sustain and may better support training performance, hunger management, and lean mass retention. Faster rates can create a large deficit, especially for smaller or less active people. The calculator limits the displayed target to at least 1,200 calories, but this general floor is not proof that a plan is nutritionally adequate. Energy needs vary, and many people require a higher minimum to obtain sufficient protein, essential fats, fiber, vitamins, and minerals. The timeline divides the planned weight difference by the selected weekly rate. Treat it as an estimate rather than a deadline. Metabolic adaptation, changes in activity, inconsistent tracking, menstrual cycles, sodium, and carbohydrate intake may alter the observed pace. Use weight averages collected under similar conditions and evaluate progress over several weeks. If the average trend stalls, a small adjustment to food intake or activity is usually more informative than a drastic change. Weight loss is not appropriate for everyone. Children, pregnant or breastfeeding people, people with a history of disordered eating, and those with medical conditions should seek individualized guidance. Medicines and illness can also influence appetite, fluid balance, and metabolism. A registered dietitian or clinician can help select a safe rate and monitor health. This calculator is an educational planning aid and not a medical diagnosis or treatment plan.