How many calories per day and how to work out your number

Your calorie number is the starting point for almost every goal, because weight change follows from it. Most adults burn somewhere between 1,800 and 2,800 kcal a day. The exact figure depends on sex, weight, height, age and activity. This guide walks through the whole calculation with a worked example, shows how to adjust the number for your goal, and explains what to do when the scale stops responding.

Start with maintenance

Maintenance is the number of calories at which your weight stays the same. It is the sum of three parts. The largest is your basal metabolic rate, the energy your body uses at complete rest for breathing, circulation and repair - roughly 60-70% of the total for most people. The second part is movement: training, walking and all the small daily activity you barely notice. The third is digestion itself, which uses up around 10% of the calories you eat. Every other target - losing fat, holding steady, building muscle - is calculated from maintenance, so it is worth getting this number right first.

The Mifflin-St Jeor equation

The calorie and macro calculator uses the Mifflin-St Jeor equation, published in 1990 and still the most widely applied formula for estimating resting energy needs (Mifflin et al., 1990). It is simple enough to do on paper:

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

The result is your basal metabolic rate. To turn it into maintenance, multiply by an activity factor.

Choosing the activity factor

• Desk job, no training: about 1.2
• Light activity, training 1-3 times a week: about 1.4
• Moderate activity, training 3-5 times a week: about 1.55
• Hard training 6-7 times a week: about 1.7
• Physical job plus daily training: up to 1.9

The most common mistake in the whole calculation is picking a factor that is too high. Three workouts a week do not make a desk worker "very active". When in doubt, choose the lower factor - it is easier to add calories later than to wonder why the deficit is not working. The calculator picks the factor from your training days automatically.

A worked example

A 30-year-old man, 80 kg and 180 cm: 10 × 80 + 6.25 × 180 - 5 × 30 + 5 = 1,780 kcal at rest. He trains four times a week and sits the rest of the day, so 1.55 fits: 1,780 × 1.55 is about 2,760 kcal to maintain his weight.

More reference points:

• A 30-year-old woman, 65 kg, 168 cm, training three times a week: about 2,150 kcal.
• The same 80 kg man with a desk job and no training: about 2,140 kcal.

Calories by goal

• Fat loss: subtract 300-500 kcal from maintenance. That pace drops roughly 0.5-1% of body weight a week (more in how to lose weight healthily).
• Maintaining: eat around maintenance and check your weight weekly.
• Muscle gain: add 250-500 kcal (more in nutrition for muscle growth).

A bigger deficit is tempting but usually backfires: hunger grows, training quality drops, more muscle is lost along with the fat, and the diet becomes hard to stick to. A moderate deficit you can hold for months beats an aggressive one you abandon in three weeks.

Why calculators disagree

Equations and activity factors differ, so two calculators can land 10-15% apart. That is normal. Every formula predicts the average person of your size, and you are not an average - your genetics, muscle mass and daily movement all shift the real number. The estimate is a starting point, not a measurement. What matters far more is how your body responds over the next few weeks.

Your body adapts

Maintenance is not fixed. As you lose weight, a lighter body simply burns less, and on top of that the body becomes more economical during a long diet - it moves less without you noticing and spends less energy on the same work. Researchers call this metabolic adaptation (Trexler et al., 2014). In practice it means the deficit that worked in month one can stop working after 5-10 kg. That is not a broken metabolism - it is the signal to recalculate from your new weight.

What to do with the number

Hold it for two or three weeks. Weigh yourself a few times a week under the same conditions - in the morning, after the bathroom, before food - and judge only the weekly average, because day-to-day weight swings by a kilogram or more on water alone. If the average is not moving the way you want, adjust by 100-200 kcal and wait another two weeks. Set your protein target separately, because it follows your body weight rather than your calories (see how much protein you need per day).

When to recalculate

Redo the calculation when your weight has changed by around 5 kg, when your training or job activity changes, or when progress has stalled for more than three weeks despite honest tracking. Small day-to-day fluctuations are noise - do not chase them.

Common mistakes

• Overstating the activity factor and eating a phantom deficit
• Judging by single weigh-ins instead of the weekly average
• Cutting calories aggressively, stalling, then cutting even harder
• Forgetting liquid calories, sauces and weekend meals in the count
• Never recalculating after losing or gaining weight

Frequently asked questions

How many calories per day does a woman need?

Most adult women maintain their weight on roughly 1,800-2,200 kcal a day. An active 65 kg woman who trains three times a week lands around 2,150 kcal, while a sedentary office day pulls the number closer to 1,700-1,800. Height, weight and age move it further, so calculate your own rather than borrowing an average.

How many calories per day does a man need?

Most adult men fall between 2,200 and 2,800 kcal. An 80 kg man training three or four times a week maintains at about 2,760 kcal; the same man without training needs closer to 2,140 kcal. The difference is almost entirely activity.

How many calories should I eat to lose weight?

Your maintenance minus 300-500 kcal. For most women that means roughly 1,400-1,800 kcal, for most men 1,800-2,300 kcal - but the honest answer always starts from your own maintenance number, not from a universal figure.

Is it safe to eat less than 1,200 kcal a day?

Not without medical supervision. Very low targets make it nearly impossible to cover protein, iron and other basics, accelerate muscle loss and rarely hold for long. If your calculated deficit lands that low, take the slower route: a smaller deficit plus more daily movement.

Do I have to count calories every day?

No. Counting for the first few weeks teaches you what your portions actually contain, and after that many people manage with consistent meals and a weekly look at the scale. Count again for a while whenever progress stalls, because untracked calories are the usual culprit.

Why is my weight not dropping on the calculated deficit?

Nine times out of ten the deficit exists on paper only: the activity factor was too generous, or snacks, drinks and weekends did not make it into the count. Water retention can also mask fat loss for two or three weeks, especially after starting training. Track honestly for two more weeks, judge the weekly average, and only then cut a further 100-200 kcal.

From a number to a full plan

Tavo Programa works out your calorie and macro targets and turns them into a weekly meal plan with concrete meals and portions.

Read next: How to lose weight healthily, Nutrition for muscle growth and How much protein you need per day.