A 35-year-old man who is 178 cm and 80 kg and lightly active needs about 2,400 calories a day to maintain his weight. To lose roughly half a kilo a week he would eat about 500 calories less, around 1,900 kcal. The calculator uses the Mifflin-St Jeor equation and multiplies the result by an activity factor.
How do you calculate your daily calorie needs?
Your body burns energy in two main ways: your basal metabolic rate (BMR), the calories you use at rest for your heart, brain and breathing, and the extra energy you burn through movement and digesting food. This calculator estimates BMR with the Mifflin-St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men or − 161 for women. It then multiplies by an activity factor between 1.2 for a desk-bound routine and 1.9 for extreme activity. The result is called your total daily energy expenditure, or TDEE.
How many calories should you eat to lose weight?
A kilogram of body fat holds roughly 7,700 kcal, so a daily deficit of 500 kcal produces about 0.45 kg of fat loss per week in theory. Real life is messier. Your weight swings with water, salt and your cycle, and your needs fall as you get lighter. Give any new target two to three weeks, look at the average trend on the scale and adjust intake by 100 to 200 kcal if progress stalls.
Avoid going below 1,500 kcal for men or 1,200 kcal for women without professional guidance. The calculator warns you when your target drops under those lines. If you also want to keep muscle while dieting, make sure you eat enough protein, which you can work out with the Protein Calculator, and lift weights.
Macros: protein, fat and carbohydrates
As a starting point the tool allots 1.8 g of protein per kilogram of body weight, 25% of calories from fat and the rest from carbohydrates. That is a flexible split that suits most people. It is a starting point, not a diet, so adjust it to what keeps you full and satisfied.
How accurate is a calorie calculator?
- The estimate is usually within about 10% for healthy adults, which means two people with identical numbers can differ by 200 kcal a day.
- Pregnancy, thyroid conditions, some medicines and eating disorders fall outside the model, so ask a doctor or dietitian for guidance.
- The formula is not meant for children and teenagers under 18.
Want to see how training affects your body composition? Try the FFMI Calculator for lean mass, estimate your strength with the Bench Press Calculator, or plan running fuel with the Running Pace Calculator.
How to use this calculator
- Select your sex and enter age, height and weight.
- Choose the activity level that honestly matches your week.
- Pick your goal: lose, maintain or gain weight.
- Press Calculate to see your calorie needs, your goal in kcal and a starting split of protein, fat and carbohydrates.
Key figures at a glance
| Formula | Mifflin-St Jeor × activity factor |
|---|---|
| 1 kg of fat | about 7,700 kcal |
| Safe minimum without supervision | 1,500 kcal (men), 1,200 kcal (women) |
| Protein starting point | 1.8 g per kg |
Frequently asked questions
It depends on your sex, age, height, weight and activity. An average woman needs roughly 2,000 kcal and an average man roughly 2,500 kcal a day to maintain weight.
Subtract 300 to 500 kcal from your maintenance calories. That gives about 0.25 to 0.5 kg of weight loss per week.
Total daily energy expenditure: all the calories you burn in a day, including exercise and daily movement.
It is one of the most accurate estimation equations for adults, typically within about 10% of measured values.
No. Counting for a few weeks can teach you portion sizes, but many people prefer simple habits such as more protein and vegetables.