Calorie and Macro Calculator: Your Daily Target

How the calculation works#

The target is built in three steps, and each one adds its own uncertainty.

Step one — basal metabolic rate. This is what your body spends lying still all day: breathing, heart, kidneys, brain. It accounts for 60–70% of everything you burn. The calculator uses the Mifflin-St Jeor equation:

Men: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5 Women: 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

If you enter a body fat percentage, it switches to Katch-McArdle, which works from lean mass and therefore does not ask about sex:

370 + 21.6 × lean mass(kg)

Step two — activity. The basal rate is multiplied by a factor between 1.2 and 1.9. This is where the estimate loses the most accuracy, as below.

Step three — the goal. A deficit or surplus matching your chosen pace is applied, treating a kilogram of fat tissue as 7700 kcal.

Activity is the largest source of error#

The difference between "moderate" and "high" on this scale is around 300 kcal a day. That is more than any rearrangement of macronutrients can give you, and more than the error of the equation itself.

People overestimate their level consistently: three runs a week feels like high activity, yet it adds under two hundred kilocalories a day. An hour of lifting burns 250–400 kcal — about one chocolate bar, not a free dinner.

There is a second trap: compensation. After training, people unconsciously move less for the rest of the day — standing up less, walking slower, sitting longer in the evening. The real increase in daily burn is therefore almost always smaller than a watch reports.

A practical rule: if you are torn between two levels, take the lower one. Erring low costs you slightly slower progress. Erring high costs you all of it, plus the conclusion that "these calculators do not work."

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Where the macro numbers come from#

The calculator does not split calories evenly or by any fashionable ratio. It allocates them in a strict order of priority: protein first, a floor of fat second, carbohydrates get the remainder.

Protein comes first because it determines what the weight you lose or gain is made of.

Goal	Protein, g per kg	Basis
Maintenance	1.6	Muscle-gain plateau in the Morton 2018 meta-analysis
Fat loss	2.0	Protecting lean mass in a deficit, Helms 2014
Muscle gain	1.8	More adds nothing but crowds out the rest of the diet

Fat gets a floor of 0.8 g per kg of body weight, and around 28% of calories by default. The floor is not cosmetic: too little dietary fat impairs sex hormone synthesis and the absorption of vitamins A, D, E and K. The slider moves the share between 20% and 40% — that range is about what suits you, not about effectiveness.

Carbohydrates take whatever is left. They are neither harmful nor optional; they are simply last in the queue, because they are the only macronutrient with no established minimum. They also fuel training, and hard sessions feel distinctly worse on very low carbohydrate intakes.

If protein and fat leave almost nothing for carbohydrates, that is a sign of too steep a deficit rather than clever macro splitting — the calculator says so directly.

Читайте также: How much protein you actually need per day

On pace and the 7700 rule#

The pace slider stops at 1% of body weight per week, and not out of timidity. Garthe et al. (2011) had athletes lose weight at two rates, one twice as fast as the other. Both groups lost weight, but the faster group gave up noticeably more lean mass and strength. Faster means a larger share of what you lose is not fat.

The "7700 kcal = 1 kg" rule itself holds up over a week or two and falls apart over months. It assumes constant expenditure, and expenditure falls: a lighter body costs less to move, and adaptive thermogenesis adds to that. Modelling by Hall et al. (Lancet, 2011) shows the real curve is considerably flatter than the linear one, and that a plateau arrives not because "metabolism broke" but because burn has descended to meet intake.

So treat the forecast here as the earliest possible date. Expect it to take 20–30% longer in practice — that is the normal course of events, not your failure.

Читайте также: Why the scale stopped: what happens on a plateau

What the calculator does not know#

It does not know your genetics, your thyroid, your medication or how you sleep. It ignores NEAT — the incidental movement outside training that varies by hundreds of kilocalories between people and drops measurably in a deficit. It does not model adaptive thermogenesis, and it has no idea about situations where calculated targets do not apply at all: pregnancy and breastfeeding, a history of disordered eating, kidney disease, GLP-1 medication.

Above all, it does not know how much you actually eat. That is not a footnote: in the Lichtman study, participants sincerely convinced their problem was metabolic were underreporting intake by nearly half while overestimating their exercise. No equation survives unlogged cooking oil, the last third of a child's dinner, and weekends that "do not count."

How to use the number#

Treat the result as a hypothesis. Eat it for two weeks, weighing yourself under identical conditions — morning, after the bathroom, before food — and read the weekly average rather than individual days: water swings of ±1.5 kg are routine and have nothing to do with fat.

If two weeks moved the scale in the right direction at roughly the expected speed, the target is right. If nothing moved, take off 150–200 kcal, not a third of your food. If it moved faster than planned, add the same amount back: losing too fast is also an error, it just looks more flattering for the first month.

Come back to the calculator after a 4–5 kg change. By then the numbers are out of date — burn is calculated from your current mass, and your current mass is no longer the one you entered.