Calorie Calculator

How it works

Daily calorie needs start with your basal metabolic rate, estimated here with the Mifflin-St Jeor equation (10 x weight in kg + 6.25 x height in cm - 5 x age, plus 5 for men or minus 161 for women). Multiplying BMR by your activity factor gives total daily energy expenditure, the maintenance level at which your weight stays roughly stable. The goal then adjusts the target: this calculator subtracts 500 kcal per day for weight loss and adds 300 kcal for weight gain. The 500 figure comes from the classic estimate that a pound of stored body fat represents about 3,500 kcal, so a 500 kcal daily deficit is roughly one pound per week. Real losses are not perfectly linear: early weeks include water shifts, and the body adapts over time. For gaining, a smaller surplus of about 300 kcal favors leaner gains with less fat when combined with resistance training. Treat the numbers as a starting estimate, accurate for most people within about 10 percent, then calibrate with the scale: if two to three weeks at a target produce no trend, adjust by 100 to 200 kcal and reassess.