Calorie Calculator
Estimate how many calories you burn in a day. The calculator works out your resting needs (basal metabolic rate) with the Mifflin–St Jeor equation, adjusts for your activity level to get the calories that maintain your weight, and shows calorie targets for losing or gaining weight gradually.
Used only in the formula.
18 to 100.
Result
Enter your height, weight and age to estimate your daily calories.
The calculation runs in this browser tab. Nothing you enter is uploaded, saved or logged.
What are BMR and daily calorie needs?
Your basal metabolic rate (BMR) is the energy your body uses at rest to keep you alive: breathing, circulation, temperature, and cell repair. It is typically the largest part of your daily energy use. Your total daily energy expenditure (TDEE) is the BMR multiplied by an activity factor, from 1.2 for a sedentary life to 1.9 for very hard physical work or training.
Eating roughly the calories of your TDEE keeps your weight steady. Eating less produces a gradual loss and eating more a gradual gain. A common rule of thumb is that about 7,700 kilocalories equal one kilogram of body weight (3,500 per pound), so a daily deficit of 500 kcal is about 0.45 kg a week. The rule is only approximate, because the body adapts as weight changes.
How to use the Calorie Calculator
- Choose metric or US units and enter your height and weight.
- Choose your sex and enter your age. Both are used in the equation.
- Choose the activity level that best matches an ordinary week.
- Read your maintenance calories and BMR, then the table of calorie targets with the approximate weekly change.
Formula
- BMR for men
- BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- BMR for women
- BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
- Maintenance
- TDEE = BMR × activity factor (1.2, 1.375, 1.55, 1.725 or 1.9)
- Weekly weight change
- kg per week = daily calorie difference × 7 ÷ 7,700
The Mifflin–St Jeor equation was published in 1990 and is widely used in nutrition practice because it predicts the resting energy of many healthy adults within about 10%, though not all.
The activity multipliers are the classic values; choose the level you actually sustain, not the one you aim for.
Worked example
A 35-year-old woman, 170 cm tall, weighing 68 kg, with light exercise 1–3 days a week. These are the results the calculator gives:
| Question | Result |
|---|---|
| Input: Units | Metric (centimetres, kilograms) |
| Input: Height | 170 cm |
| Input: Weight | 68 kg |
| Input: Sex | Female |
| Input: Age | 35 years |
| Input: Activity level | Light: exercise 1–3 days a week |
| Calories to maintain your weight | 1,934 kcal per day |
| Resting needs (BMR) | 1,407 kcal per day |
| Activity multiplier | × 1.375 |
| Formula | Mifflin–St Jeor |
Assumptions and limits
- The result is an estimate. Individual needs can differ from it by several hundred calories because of body composition, genetics, health and hormones.
- The formula is for healthy adults aged 18 to 100. It is not for pregnancy, breastfeeding, children and teenagers, or people with medical conditions.
- Targets that fall below your resting needs are flagged. Eating below your BMR for long is not recommended without medical supervision.
- The weekly change uses the approximation of 7,700 kcal per kilogram; real weight change depends on many factors and slows down over time.
- This is not medical or dietary advice. Talk to a doctor or a registered dietitian before changing your diet or weight.
Frequently asked questions
How many calories should I eat a day?
To keep your weight, about your maintenance calories, which depend on your size, age, sex and activity. The calculator estimates this number; for a 35-year-old woman of 170 cm and 68 kg who exercises lightly it is about 1,934 kcal.
What is BMR?
The basal metabolic rate: the calories your body burns at complete rest. The calculator shows it separately, because it is the floor under your daily needs.
How many calories do I need to lose weight?
Eat fewer calories than you burn. A deficit of about 500 kcal a day corresponds to losing roughly 0.45 kg (1 lb) a week according to the common rule of thumb. A smaller deficit of 250 kcal is gentler and easier to sustain.
Why is there a warning below my BMR?
Because eating less than your resting needs for long can lead to nutrient shortfalls and loss of muscle. If a target is marked below your resting needs, speak to a doctor or dietitian before following it.
Which activity level should I choose?
Pick the one that matches an average week. People tend to overestimate their activity: most office workers who exercise a few times a week are in the “light” or “moderate” group.
Is the Mifflin–St Jeor equation accurate?
It is one of the more reliable equations for healthy adults and is within about 10% for many people, but it is still an average. Track your weight over two or three weeks and adjust the calories to what actually happens.