Calorie Calculator
This calorie calculator estimates how many calories you need per day and what to eat for your weight goal. Example: a 30-year-old man, 175 cm and 75 kg, lightly active, needs about 2,599 kcal and should eat 2,049 kcal to lose 0.5 kg a week.
Source: Mifflin-St Jeor, Mifflin MD, St Jeor ST et al. (1990): A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 51(2):241–247. Updated: .
How it is calculated
A calorie calculator estimates two numbers: the energy your body uses in a day, and the intake that moves your weight in the direction you want. Eat as much as you burn and your weight stays put; eat less and you lose, eat more and you gain.
Formulas
Basal metabolic rate (BMR) by Mifflin-St Jeor: 10 × weight in kg + 6.25 × height in cm − 5 × age, plus 5 for men or minus 161 for women. Daily needs = BMR × activity factor, from 1.4 for a sedentary life to 2.4 for heavy physical work; the steps follow the lifestyle ranges of the FAO/WHO/UNU report on human energy requirements. Target = daily needs ± weekly weight change × 7,700 kcal ÷ 7.
Worked example
A man aged 30, 175 cm, 75 kg: BMR = 750 + 1,093.75 − 150 + 5 = 1,699 kcal. With a sitting job and some walking (×1.53) he needs 2,599 kcal a day. To lose 0.5 kg a week he has to save 0.5 × 7,700 ÷ 7 = 550 kcal a day, so the target is 2,049 kcal. Losing 0.75 kg a week would mean 1,774 kcal, gaining 0.25 kg a week 2,874 kcal.
A woman of 30, 165 cm and 65 kg has a BMR of 1,370 kcal and needs 2,096 kcal at the same activity level; 0.5 kg a week brings her to 1,546 kcal. For 0.75 kg or 1 kg a week she would have to eat less than her BMR, so the calculator shows no target for those paces.
Lower limit: no target below your BMR
The calculator gives no target below your basal metabolic rate, and none below 1,200 kcal a day for women or 1,500 kcal a day for men; the table shows a dash instead. Lower intakes belong under the supervision of a doctor or dietitian.
How to read the result
- The 7,700 kcal per kilogram of body fat (3,500 per pound) is a rule of thumb. In practice weight loss slows down, because a lighter body burns less.
- Pick the activity level honestly – most desk workers are at 1.4 to 1.53 even with a few workouts a week.
- Check your weight after two to three weeks and adjust the calories rather than trusting the number blindly.
Frequently asked questions
How many calories should I eat a day?
It depends on sex, age, size and activity. The example man needs about 2,599 kcal to keep his weight; the example woman about 2,096 kcal.
How many calories do I need to cut to lose weight?
Roughly 550 kcal a day for 0.5 kg a week, and 1,100 kcal a day for 1 kg a week, based on 7,700 kcal per kilogram of fat.
Which formula does the calculator use?
The Mifflin-St Jeor equation from 1990, which is widely used for healthy adults, multiplied by an activity factor.
Is it safe to eat below my basal metabolic rate?
For a short time many people tolerate it, but a long-term intake below your BMR makes it hard to cover nutrients and should be supervised by a doctor or dietitian. The calculator shows no target in that case.
Why do I lose weight more slowly than calculated?
Because energy needs fall as you get lighter, and early losses include water. The rule of thumb overstates long-term loss; re-enter your new weight every few weeks.
Sources and legal basis
- Mifflin-St Jeor: Mifflin MD, St Jeor ST et al. (1990): A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 51(2):241–247
- FAO/WHO/UNU 2004: FAO/WHO/UNU (2004): Human energy requirements – Report of a Joint Expert Consultation, Chapter 5, Table 5.1 (PAL ranges by lifestyle)
- Hall KD (2008): What is the required energy deficit per unit weight loss? Int J Obes 32:573–576 (limits of the 7,700 kcal rule of thumb)
- Harvard Health Publishing (Harvard Medical School): Calorie counting made easy – intake not below 1,200 kcal (women) or 1,500 kcal (men) without professional supervision (accessed 5 Oct 2026)
- MedlinePlus (U.S. National Library of Medicine, NIH): Diet for rapid weight loss – Low-Calorie Diet 1,200–1,500 kcal (women), 1,500–1,800 kcal (men), only under supervision (accessed 5 Oct 2026)
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