Calorie & TDEE Calculator

BMR and TDEE are not the same number

BMR — basal metabolic rate — is the energy your body uses doing nothing at all: keeping your heart beating, your brain running, your temperature stable. For most adults it is 60–70% of everything they burn in a day. Eating at your BMR is not a diet; it is what a body needs in a coma.

TDEE — total daily energy expenditure — is BMR multiplied by an activity factor covering movement, exercise and the energy cost of digesting food. This is your maintenance level, and every goal is set relative to it.

The activity multiplier is the least precise part of the whole calculation, and it is the part you control. Overstating it by one level typically inflates the target by 300–400 calories, which is enough to turn a deficit into maintenance.

How fast is realistic

A kilogram of body fat holds roughly 7,700 calories, so a 550-calorie daily deficit is about half a kilo a week, or a pound and a bit. That is the fastest rate most people can hold without losing muscle, feeling awful and eventually rebounding.

Faster is not better. Aggressive deficits cost lean mass, tank training performance, and are abandoned. A 275-calorie deficit — a quarter kilo a week — is slower on paper and far more likely to still be happening in six months.

Gaining follows the same logic in reverse. A surplus much above 300 calories a day mostly adds fat, not muscle, because muscle can only be built so quickly however much you eat.

Why the number is an estimate

Predictive equations land within about 10% of measured expenditure for most adults, which is close enough to start from. They are least accurate for people at the extremes of body composition: a bodybuilder burns more than the formula predicts because muscle is metabolically active, and someone carrying a great deal of fat burns less.

They are also blind to genetics, thyroid function, medication, sleep, and how much you fidget — which varies between individuals by hundreds of calories a day. Treat the result as a starting hypothesis, weigh yourself over two or three weeks, and adjust by 100–200 calories based on what actually happens to the trend.

Protein, fat and the rest

Total calories decide whether weight moves. Composition decides what kind of weight. Protein at roughly 1.6 grams per kilogram of body weight protects muscle in a deficit and keeps you full — the single most useful adjustment most people can make.

Fat should stay above about a quarter of calories, because it is needed for hormone production and for absorbing several vitamins. Carbohydrate fills the remainder and fuels training. Below those two floors, the split is a matter of preference, and the diet you can keep to beats the one that is theoretically optimal.

Where the floor comes from

This calculator will not recommend below about 1,200 calories a day for women or 1,500 for men. Those are the widely-used clinical thresholds below which it becomes difficult to obtain adequate micronutrients from food, and below which supervised support is appropriate.

If your calculated target hits that floor, the honest answer is that the goal is too aggressive for your body size. A smaller deficit combined with more movement gets there without the harm.