Fitness calculator
Calorie Calculator
Calculate your daily calorie needs using the Mifflin-St Jeor formula. Estimate your basal metabolic rate (BMR), adjust for your activity level, and find calorie targets for weight loss or gain.
Maintenance calories
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How the calorie calculator works
Your daily calorie needs depend on two things: your basal metabolic rate (BMR), which is the energy your body uses at rest, and your activity level, which accounts for exercise and daily movement. The calculator multiplies your BMR by an activity factor to estimate your total daily energy expenditure (TDEE) — the calories you burn on an average day. From there you can estimate calorie targets for losing or gaining weight.
The Mifflin-St Jeor formula
The Mifflin-St Jeor equation is the most widely used and accurate of the common BMR formulas. It was developed in 1990 using modern data and is consistently more accurate than older formulas like Harris-Benedict.
For example, a 25-year-old man who is 180 cm tall and weighs 80 kg would have a BMR of (10 × 80) + (6.25 × 180) − (5 × 25) + 5 = 1,805 kcal/day. At a moderate activity level (×1.55), his TDEE would be 1,805 × 1.55 = 2,798 kcal/day. A 30-year-old woman who is 165 cm tall and weighs 60 kg would have a BMR of (10 × 60) + (6.25 × 165) − (5 × 30) − 161 = 1,320 kcal/day, and at the same moderate activity level, a TDEE of 1,320 × 1.55 = 2,046 kcal/day.
Activity multipliers
The activity level adjusts your BMR to account for exercise and daily movement. These multipliers represent how much total energy you expend above your resting rate:
Most people overestimate their activity level. If your goals are not being met, try a lower activity category and reassess after 2–4 weeks.
- Sedentary (×1.2): Little or no exercise, mostly desk work or very sedentary lifestyle
- Lightly active (×1.375): Exercise 1 to 3 days per week
- Moderately active (×1.55): Exercise 3 to 5 days per week or a job that involves standing and walking
- Very active (×1.725): Exercise 6 to 7 days per week with intensity
- Extra active (×1.9): Physical job combined with regular intense training
Calorie targets for losing or gaining weight
A deficit of approximately 500 calories per day leads to a weight loss of about 0.5 kg (1 lb) per week, and a surplus of 500 calories per day leads to a gain of about the same. These are approximations based on the assumption that 7,700 calories roughly equal 1 kg of body weight. In practice, your actual results depend on metabolism, exercise, diet quality, and other factors.
Very low calorie intakes below roughly 1,200 kcal per day for most adults should not be attempted without medical supervision, as they risk nutrient deficiency and may slow metabolism. These estimates are starting points; adjust your intake based on real-world results over 2–4 weeks and how you feel. This calculator provides estimates for healthy adults and is not medical advice. It is not intended for children, pregnant or nursing individuals, or people with medical conditions — consult a healthcare provider in those cases.
Frequently asked questions
How many calories should I eat a day?
It depends on your size, activity level, and goals. This calculator estimates your maintenance calories (TDEE) based on the Mifflin-St Jeor formula. To lose weight, eat fewer calories; to gain weight, eat more. Most people find a deficit or surplus of 300–500 calories per day to be sustainable.
What is the difference between BMR and TDEE?
BMR (basal metabolic rate) is the calories your body burns at rest just to maintain basic functions like breathing and circulation. TDEE (total daily energy expenditure) is your BMR multiplied by an activity factor to account for exercise and daily movement. TDEE is what you use for diet planning because it reflects your real energy needs.
How accurate is Mifflin-St Jeor?
Studies show Mifflin-St Jeor is within about ±10% for most healthy adults, making it the most accurate of the common BMR equations compared by the American Dietetic Association. However, individual metabolism varies due to genetics, hormones, muscle mass, and body composition, so these are estimates to adjust based on your real results over time.
How many calories do I need to lose or gain 1 kg or 1 lb?
Approximately 7,700 calories equal 1 kg of body weight, and 3,500 calories equal 1 lb. So a deficit of 500 kcal/day leads to roughly 0.5 kg (1 lb) of loss per week. This assumes stable metabolism and normal circumstances; real results vary based on individual factors.
Should I eat back exercise calories?
Your activity level is already factored into your TDEE estimate, so your target is the total you should aim for each day, including exercise. You do not need to 'eat back' extra calories on top of your target. However, if your estimates do not match your real results after 2–4 weeks, adjust your activity level or intake accordingly.