Calorie Calculator

From BMR to daily calories

Your body burns energy even at complete rest — keeping you warm, breathing and thinking. That resting burn is your basal metabolic rate, and the Mifflin-St Jeor equation estimates it from sex, age, height and weight: for men, 10 × weight in kg + 6.25 × height in cm − 5 × age + 5; for women the same formula with −161 instead of +5. A 35-year-old woman who is 165 cm and 68 kg has a BMR of about 1,375 kcal a day.

BMR is only the floor. Everything else you do — walking to work, exercising, even fidgeting — adds on top, which is why the calculator multiplies BMR by an activity factor to reach TDEE, the number of calories that holds your weight steady. The same woman, moderately active, lands at about 2,131 kcal a day: that is her maintenance level, and the number every weight goal is measured against.

Activity levels, honestly chosen

The activity factor is where most calorie calculators go wrong, because people overestimate how active they are. Sedentary (1.2) means a desk job with little exercise; lightly active (1.375) is light exercise one to three days a week; moderately active (1.55) is moderate exercise three to five days; very active (1.725) is hard exercise six or seven days; extra active (1.9) is a physical job or twice-daily training. Pick the level that describes a typical week, not your best week — a single gym session does not move you up a band.

If your weight is stable and you eat roughly the calculator's maintenance figure, the estimate is about right for you. If you are steadily gaining or losing on a known intake, trust the scale over the equation: adjust the target by the size of the drift, in steps of 100–200 kcal, and give each change two to three weeks before judging it.

Setting a target for your goal

For weight loss the calculator subtracts 500 kcal from maintenance, a deficit that typically produces around half a kilogram a week; for weight gain it adds 500. Those round numbers are starting points, not prescriptions: a smaller deficit is easier to sustain and preserves more muscle, and anyone with a medical condition, a history of disordered eating, or a target below about 1,200 kcal a day should set the plan with a clinician or dietitian rather than a calculator.

Calories are only half the story. Two diets at the same calorie level can feel very different: protein and fibre keep you full longer, liquid calories barely register, and sleep and stress move appetite more than most people expect. Use the calculator's number as a budget, then judge the plan by hunger, energy and the trend on the scales over weeks, not by any single day's total.