Calorie Calculator

The calorie calculator estimates your daily energy needs with the Mifflin-St Jeor formula. Enter your gender, age, height, weight and activity level – the calculator shows the calorie intake to maintain your weight, safe targets for losing and gaining, and your daily protein, fat and carbohydrate targets in grams.

Why know your calorie needs

Calories are the body’s fuel: we take them in with food and spend them on everything from heartbeat to workouts. When intake exceeds spending, weight goes up; when it falls short, weight goes down. Knowing your number turns weight control from guesswork into arithmetic: not “eat less” but “eat 300–500 kcal below your norm”. It is the main tool for losing fat, gaining muscle or simply staying in shape without crashes.

How to use the calculator

Enter your gender, age, height and weight, then choose your activity level – honestly rate your typical day, not your best one. The result shows three numbers: the intake to maintain weight, the target for losing (−15%) and for gaining (+15%). Below, protein, fat and carbohydrate targets are calculated in grams as a guide for building meals. The table shows how the norm changes with different activity.

The Mifflin-St Jeor formula

Since 1990 this has been the standard formula in dietetics. Basal metabolic rate (BMR) – the energy spent at rest: for men BMR = 10 × weight + 6.25 × height − 5 × age + 5; for women the same but −161. Daily needs (TDEE) = BMR × activity factor: from 1.2 for a sedentary lifestyle to 1.9 for heavy physical work. For example, a 30-year-old man at 80 kg and 180 cm with an office job burns about 2136 kcal a day.

How to lose or gain weight safely

Sustainable weight loss is a 15–20% deficit: at this pace you lose 0.5–1 kg per week without triggering “survival mode”. Deficits above 25% often cause crashes, muscle loss and a slower metabolism. Gaining works the other way round: a 10–15% surplus with enough protein (1.6–2 g per kg of body weight) and strength training. Weigh yourself once a week under the same conditions and adjust your intake by 100–200 kcal if your weight stalls for a month.

Protein, fat and carbohydrates

The calculator splits the norm into nutrients: 25% protein, 30% fat, 45% carbohydrates. Protein is the building material for muscles and enzymes – at least 1.2–1.6 g per kg. Fat supports hormones and vitamin absorption – going below 0.8 g per kg is unwise. Carbohydrates are the main energy source and the easiest macro to adjust first. This is a starting point: with training, protein goes up to 30%; extreme ratios should not be tried without a doctor.

Limitations of the calculation

The formula gives a statistical estimate with about ±10% error: people with different metabolisms and muscle mass get different numbers. Pregnant and breastfeeding women, teenagers, people with thyroid conditions and significant obesity should have their norm set by a doctor. Also remember: food calorie tables are averages, and portion-counting errors easily reach 20%.

This calculation is for information only and is not medical advice. Consult a doctor before changing your diet.

Frequently asked questions

How is the calorie norm calculated?
The calculator uses the Mifflin-St Jeor formula: it derives your basal metabolic rate (BMR) from weight, height, age and gender, then multiplies by an activity factor from 1.2 to 1.9. The result is your daily intake to maintain weight.
How many calories do I need to lose weight?
Usually 15–20% below your norm – for most people that is 300–500 kcal. At this deficit you lose 0.5–1 kg per week without crashes or muscle loss. Harder diets work worse in the long run: metabolism slows down and the weight comes back.
How accurate is the Mifflin formula?
The error is about ±10% for most people. You check it in practice: weigh yourself weekly on a stable diet – if your weight has not changed for a month, the norm is right. Otherwise adjust by 100–200 kcal.
How much protein, fat and carbs do I need per day?
The calculator gives a starting split of 25/30/45: protein about 1.6–2 g per kg of body weight, fat at least 0.8–1 g, carbs make up the rest. With strength training, raise protein; with low activity, trim carbs.
Why has my weight stopped dropping on a diet?
Most often the body has adapted and slowed its metabolism, or intake has quietly crept up (portions, snacks, drinks). Fix: recalculate the norm for your new weight and add 1–2 thousand steps a day. Water retention can also hide progress – look at the 2–3 week trend, not a single day.
Is it safe to eat under 1200 kcal a day?
No – without medical supervision it is dangerous: such a deficit almost always means muscle loss, hair loss, hormonal problems and rapid weight regain. For most women the safe lower bound is 1400–1600 kcal, for men 1800–2000.

Updated: Oct 12, 2026

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