Calorie calculator
Estimate how many calories your body uses each day, from your age, height, weight and activity, with the Mifflin-St Jeor equation.
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About you
Your daily calories
To keep your weight stable
— kcal a day
Choose the sex used by the formula, then enter your age, height and weight.
- Basal metabolic rate (BMR)
- —
- Activity factor
- —
| Goal | Per day |
|---|---|
| Weight loss | — |
| Mild weight loss | — |
| Keep your weight | — |
| Mild weight gain | — |
| Weight gain | — |
A common rule of thumb says that 500 kcal (about 2,100 kJ) a day adds up to about 0.5 kg (1 lb) a week. In practice, weight changes more slowly over time, because the body adapts. 250 kcal a day is a gentler change.
How it’s calculated
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age, then + 5 for men or − 161 for women. Daily calories = BMR × activity factor.
Equation: Mifflin-St Jeor (American Journal of Clinical Nutrition, 1990), for healthy adults.
What this estimate doesn’t tell you
- It’s an average. Two people with the same age, height and weight can use a few hundred calories a day more or less than each other.
- Muscle and body shape. The equation uses total weight, not muscle mass, so it can underestimate the needs of very muscular people.
- Age. It was built from adults aged 19 to 78. It isn’t used under 18 and is less certain in older age.
- Health and medicines. Thyroid problems, diabetes, some medicines, illness or recovery can change your needs.
- Pregnancy and breastfeeding. Needs change from month to month, so they aren’t estimated here.
This is an estimate for healthy adults, not medical or dietary advice. Before changing how much you eat, especially with a health condition, talk to a doctor or a registered dietitian. They can also help if food or your weight is a source of worry.
How it works
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Enter your details
Choose the sex used by the formula, then type your age, height and weight, in kilograms and centimetres or in pounds, feet and inches.
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Pick your activity level
Each level comes with everyday examples. If you hesitate between two, start with the lower one.
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Read your daily calories
See the calories that keep your weight stable, your basal metabolic rate and the figures for a gentle change, in kcal or kJ.
Frequently asked questions
How many calories do I need a day?
It depends on your size, age, sex and how active you are. The calculator first estimates your basal metabolic rate with the Mifflin-St Jeor equation, then multiplies it by an activity factor: 1.2 (sedentary), 1.375 (lightly active), 1.55 (moderately active), 1.725 (very active) or 1.9 (extremely active). For example, a 30-year-old woman who is 165 cm tall and weighs 60 kg has a basal metabolic rate of about 1,320 kcal. If she is moderately active, she uses about 2,050 kcal a day.
What is the Mifflin-St Jeor equation?
Published in 1990 by Mark Mifflin, Sachiko St Jeor and their colleagues in the American Journal of Clinical Nutrition, it estimates the energy your body uses at rest: 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years), then + 5 for men or − 161 for women. It was built from measurements of 498 healthy adults aged 19 to 78. A 2005 review in the Journal of the American Dietetic Association (Frankenfield and colleagues) found it the most reliable of the common equations, though it can still be more than 10% off for some people.
How many calories should I eat to lose or gain weight?
The calculator shows what eating 250 or 500 kcal a day less, or more, than your maintenance figure would mean. A common rule of thumb says that 500 kcal a day adds up to about 0.5 kg (1 lb) a week, but the real change is usually slower, because the body adapts. It never suggests a figure below your basal metabolic rate: going that low should only be done with medical supervision. A doctor or a registered dietitian can help you choose what suits you.
Why isn’t it calculated for teenagers or during pregnancy?
The equation was built from adults. Under 18, energy needs also depend on growth and puberty. During pregnancy and breastfeeding, they change from month to month. In both cases, a doctor, a midwife or a dietitian can give you a figure that fits.
What is the difference between kcal and kJ?
They are two units for the same energy: 1 kcal, what food labels call a “calorie”, equals 4.184 kJ. Labels in the European Union show both, and Australia and New Zealand mostly use kilojoules.
Is my data stored?
No. The calculation runs in your browser and nothing you type is sent anywhere. Only your choice of units (kg or lb, kcal or kJ) is remembered on this device.