How many calories to lose weight: the formula and a worked example

Short answer. To lose weight you have to eat less than you spend. Work out your basal metabolic rate with the Mifflin-St Jeor equation, multiply it by an activity factor, and take 10–20% off. For most women that lands at 1,400–1,800 kcal a day and for most men at 1,800–2,300, but the number is personal. The formula and a worked example are below, and you can get your own figure in the calorie and macro calculator.

Why "1,200 calories" is a bad answer

There is no universal target. Energy expenditure depends on weight, height, age, sex and how much you move. A woman of 165 cm and 60 kg at a desk and a man of 185 cm and 95 kg on a building site live in different calorie worlds. A number lifted from someone else's diary, or from a headline, is almost never yours.

There is a second problem. A target set too low works for about two weeks and then delivers cravings, fatigue and lost muscle. The job is not to eat as little as possible; it is to find a moderate deficit you can hold for months.

Step 1. Basal metabolic rate

Your BMR is what the body spends at complete rest — breathing, heart, brain, liver. The most reliable of the simple equations is Mifflin-St Jeor (1990), the one dietetic associations recommend:

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

If you think in pounds and inches, convert first: 1 kg = 2.2 lb, 1 inch = 2.54 cm.

Worked example: a woman, 30 years old, 165 cm, 70 kg. BMR = 700 + 1,031 − 150 − 161 = 1,420 kcal.

Step 2. Activity factor

Multiply the BMR by the factor that matches your life. What you get is maintenance — the intake at which your weight stays where it is.

Our example trains twice a week: 1,420 × 1.375 = 1,953 kcal, and that is her maintenance.

The classic mistake is inflating this factor. Two sessions a week on top of a desk job is "light", not "moderate". When in doubt, drop a step: underestimating what you spend is safer than overestimating it.

Step 3. The deficit

For weight loss, take 10–20% off maintenance:

• 10% — slow and almost unnoticeable, right for people with little to lose or a heavy training load.
• 15% — the sensible middle for most people.
• 20% — faster, but hunger and blowouts become likelier; do not run it longer than 8–12 weeks without a break.

Example: 1,953 − 15% ≈ 1,660 kcal a day. Expected pace, roughly 0.4–0.6 kg a week: as a rough rule a kilogram of fat is worth 7,000–7,700 kcal, and a 300 kcal daily deficit adds up to 2,100 a week.

Which deficit actually survives contact with real life is the subject of how big your calorie deficit should be.

The floor

Without medical supervision, do not go below 1,200 kcal as a woman or 1,500 as a man. If the arithmetic lands lower than that, cut the deficit to 10% and add movement instead: 8,000–10,000 steps a day is another 200–300 kcal.

Splitting the target into macros

Calories decide the direction, but the composition decides whether you are hungry the whole way:

• Protein: 1.6–2 g per kilogram while losing weight. It protects muscle and keeps you full. Detail in how much protein you need.
• Fat: not below 0.8–1 g per kilogram — hormones and fat-soluble vitamins depend on it.
• Carbs: everything left over. Favour whole grains, vegetables, fruit and beans: lower glycaemic index, more fibre.

For the woman in the example: 1,660 kcal becomes 120 g of protein (480 kcal), 60 g of fat (540 kcal) and about 160 g of carbs (640 kcal).

What to do with the number

A calculation is a hypothesis, not a verdict. Test it:

1. Eat at the calculated figure for two weeks and log everything, oil, sauces and drinks included.
2. Weigh yourself in the morning three or four times a week and read the weekly average, not individual days.
3. If weight has not moved in three weeks, take off another 100–150 kcal or add steps. If you are losing faster than 1% of body weight a week, eat a little more.

The hard part is not the formula, it is the honest logging. It gets much easier when an entry takes seconds: photograph the plate, or type "150 g of rice and a chicken thigh", and the Fat Track bot in Telegram and MAX estimates the calories and macros while you correct the portion in a reply. Values for basic foods are worth checking in the food database.

Common questions

Do I need to recalculate as I lose weight? Yes, every 4–5 kg. A lighter body spends less.

Should I add my workout calories on top? Not if the activity factor already accounts for training. Eating back what you burned is the most common reason a deficit fails.

Can I lose weight without counting? You can, but two or three weeks of counting shows you where the calories were actually hiding — usually oil, nuts, sauces and drinks.

If you want your own number right now, open the calorie and macro calculator, then run a week in the diary. The first seven days are free.