Macros Explained: How to Set Your Calories, Protein, Carbs and Fat
Tracking macros sounds like something only competitive athletes do. In reality it is just a structured way of answering two questions: how much am I eating, and what is it made of?
Here is how the numbers are actually built, from the bottom up.
Step one: your BMR
Basal Metabolic Rate is the energy your body uses at complete rest — breathing, circulation, brain function, keeping you at temperature. It is the largest part of your daily energy use for most people.
The Mifflin-St Jeor equation is what most dietitians use, because it is more accurate for modern populations than the older Harris-Benedict formula.
Step two: your TDEE
Total Daily Energy Expenditure is your BMR multiplied by an activity factor, ranging from about 1.2 for a sedentary lifestyle up to 1.9 for someone with a physical job who also trains.
Be honest here. Overestimating your activity level is the single most common reason a calorie target fails to produce results. Most people who describe themselves as "moderately active" are closer to lightly active, because an hour at the gym does not offset eight hours at a desk as much as it feels like it should.
Step three: adjust for your goal
- Fat loss — roughly 20% below TDEE
- Maintenance — TDEE
- Muscle gain — roughly 10% above TDEE
A 20% deficit produces steady loss of around 0.5–1% of body weight per week. Larger deficits work faster but are harder to sustain and cost more muscle. The surplus for gaining is deliberately smaller, because the body can only build muscle so quickly and the excess simply becomes fat.
Step four: split into macros
Protein and fat are set first, because both have genuine minimum requirements. Carbohydrate takes whatever calories remain.
- Protein is set by body weight, around 1.6 g/kg for muscle gain, higher when dieting
- Fat is usually 20–35% of total calories, supporting hormone production
- Carbohydrate fills the remainder and fuels hard training
A full worked example
A 30-year-old woman, 68 kg and 165 cm, training moderately, aiming to lose fat.
Her BMR works out at about 1,400 calories. Multiplied by a moderate activity factor of 1.55, her TDEE is about 2,170 calories. A 20% deficit puts her target at roughly 1,736 calories a day.
Splitting that: protein at 1.6 g/kg gives 109 g. Fat at 30% of calories gives 58 g. Protein and fat together account for about 956 calories, leaving 780 for carbohydrate — roughly 195 g.
So the daily target is 1,736 calories, 109 g protein, 58 g fat, 195 g carbs.
Why weight loss stalls
Two things happen, and both are normal.
First, your BMR falls as you lose weight. A smaller body costs less to run. The target you calculated at the start slowly drifts toward maintenance, which is why recalculating every 5–10 kg lost matters.
Second, water retention masks fat loss, sometimes for weeks. Glycogen, sodium, stress and menstrual cycles all move scale weight independently of fat. Judge progress on a two to three week rolling average, never on a single morning's reading.
If the average genuinely has not moved in three weeks, recalculate with your current weight and tighten your tracking before cutting calories further.
Do macros matter, or just calories?
Calories decide whether you gain or lose. Macros influence what that change is made of, and how tolerable the process feels.
The same 1,700 calories built around adequate protein, with enough fat and carbohydrate to train and think clearly, produces a very different outcome from 1,700 calories of whatever happens to be nearby. Same weight change on the scale, different body composition, very different adherence.
Consistency beats precision
You do not need to hit every macro exactly every day. Getting reasonably close, most days, for months, outperforms perfect tracking for three weeks followed by abandoning it.
Calculate your own calories and macro split with the Macro Calculator, and check your protein target against the Protein Calculator.