How Many Calories Should I Eat? A Practical Guide to Your TDEE

Most calorie advice starts in the wrong place. It offers a number — 1,500, 2,000, whatever the app suggests — without reference to the one figure that makes any of it meaningful: how much energy you actually burn.

That figure is your Total Daily Energy Expenditure, or TDEE. Everything else is derived from it. Eat at TDEE and your weight holds steady. Eat below it and you lose. Eat above it and you gain. A calorie target that is not anchored to your own TDEE is a guess dressed up as a plan.

So the first task is not choosing a diet. It is estimating maintenance, and the Calorie Calculator will do that from your sex, age, height, weight and activity level.

TDEE is built in two steps. First comes Basal Metabolic Rate — the energy your body uses staying alive at complete rest: breathing, circulating blood, maintaining temperature, running your brain and organs. For most people BMR accounts for roughly 60–70% of total daily burn, which surprises those who assume exercise dominates.

The most widely validated BMR equation is Mifflin-St Jeor, published in 1990 and still the default recommendation in clinical practice. For men it is 10×weight(kg) + 6.25×height(cm) − 5×age + 5; for women the same with −161 instead of +5.

Second comes an activity multiplier, applied to BMR to account for everything you do beyond lying still. The result is TDEE. You can see BMR on its own with the BMR Calculator, and the full picture with the TDEE Calculator.

This is where most estimates go wrong, and almost always in the same direction: people overestimate. Three gym sessions a week does not make you 'very active' if the other 165 hours are spent sitting.

A kilogram of body fat stores roughly 7,700 kcal (about 3,500 kcal per pound). That conversion gives you a straightforward way to translate a rate of loss into a daily deficit: a 500 kcal daily deficit is about 0.45 kg (1 lb) per week; a 250 kcal deficit is about half that.

For most people a deficit of 300–500 kcal a day is the sweet spot. It produces steady progress, it is small enough to leave room for adequate protein and training energy, and it is survivable for the months that meaningful change usually takes.

For gaining, a surplus of 250–500 kcal a day supports muscle growth without unnecessary fat gain. Larger surpluses do not build muscle faster; they build more fat alongside it.

There are lower bounds below which a calorie target stops being a diet and starts being a medical matter. The commonly cited floors are roughly 1,200 kcal a day for women and 1,500 for men, below which it becomes genuinely difficult to obtain adequate protein and micronutrients from food.

The Calorie Calculator will show you a target below these figures if that is what your inputs produce — deliberately, because hiding the number would be worse — but it flags it clearly. Very low calorie diets can be appropriate under medical supervision; they are not something to improvise.

If your maintenance is low enough that a sensible deficit lands under the floor, the better lever is usually increasing expenditure rather than cutting further: more daily movement, more training, and accepting a slower rate of loss.

Every calorie formula is a population average applied to an individual. Real metabolic rates vary around the prediction by roughly 10% in either direction even in healthy adults, and more in some cases. Two people with identical inputs can have genuinely different requirements.

Non-exercise activity thermogenesis — fidgeting, standing, pacing, general restlessness — varies enormously between people and is not captured well by any multiplier. It can differ by hundreds of calories a day between two people who both describe themselves as sedentary.

The correct response is not to hunt for a better formula. It is to treat the estimate as a hypothesis and test it.

Eat at your estimated target for two to three weeks, tracking reasonably carefully, and weigh yourself under consistent conditions. Compare weekly averages rather than daily readings — daily weight swings by a kilogram or more from fluid alone and will tell you nothing over short windows.

If your weekly average is falling at roughly the rate you intended, the estimate was good. If weight is flat after three weeks on an intended deficit, reduce by 150–200 kcal and reassess. If it is falling faster than about 1% of body weight per week, add calories back — that pace risks lean mass.

Three weeks is the minimum honest evaluation window. Two weeks is often enough to be misled by a shift in water balance, particularly at the start of a diet or around the menstrual cycle.

As you lose weight, your TDEE falls. A smaller body costs less to run, and there is an additional modest reduction in energy expenditure beyond what the size change alone predicts — often called adaptive thermogenesis. The deficit you started with gradually stops being a deficit.

This is the main mechanical reason weight loss plateaus, and it is entirely normal rather than a sign of failure. Recalculate every 4–5 kg (10 lb) of change rather than holding on to your starting number for months.

It is also why maintaining a loss requires attention rather than simply stopping. Returning to the intake that maintained your heavier body will, predictably, restore it.

Calories determine weight direction; they do not determine health, body composition or how you feel. A 1,800 kcal day built from adequate protein, vegetables, fibre and whole foods and a 1,800 kcal day of biscuits will move the scale identically and differ in almost every other respect.

Protein in particular deserves separate attention during a deficit, because it protects the lean mass you want to keep. The Protein Intake Calculator will give you a target, and the Macro Calculator will split your calories across protein, carbohydrate and fat.

Get maintenance right, set a modest deficit or surplus, keep protein adequate, train, and adjust on evidence. That is most of what calorie management actually is.