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Estimate how many calories you burn a day (your BMR and TDEE), and see target calories for maintaining, losing or gaining weight. This uses the Mifflin-St Jeor equation, the formula most widely recommended by dietitians for estimating calorie needs.
How to use the Calorie Calculator
Choose your sex and preferred units, then enter your age, height, weight and activity level. The calculator shows your BMR, your maintenance calories (TDEE), and target calories for mild or standard weight loss or weight gain.
What is BMR?
Basal Metabolic Rate (BMR) is roughly how many calories your body would burn in a day if you stayed completely at rest, just keeping your basic functions like breathing and circulation running. It does not include any calories burned through movement, exercise or digesting food.
What is TDEE?
Total Daily Energy Expenditure (TDEE) is your BMR plus the calories you burn through daily activity, exercise and digestion. TDEE is your maintenance calorie level: eating around this amount tends to keep your weight roughly stable over time.
The Mifflin-St Jeor formula
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
This equation, published in 1990, is widely recommended by dietitians and nutrition bodies as one of the more accurate general-purpose formulas for estimating BMR, though it remains an estimate rather than a direct measurement.
Activity levels and TDEE
To turn BMR into TDEE, multiply it by an activity factor:
| Activity level | Multiplier |
|---|---|
| Sedentary (little or no exercise) | 1.2 |
| Lightly active (light exercise 1–3 days/week) | 1.375 |
| Moderately active (moderate exercise 3–5 days/week) | 1.55 |
| Very active (hard exercise 6–7 days/week) | 1.725 |
| Extra active (very hard exercise, physical job) | 1.9 |
Choosing the activity level is the most subjective part of the calculation and the most common source of error, since most people who exercise tend to overestimate their day-to-day activity outside of workouts.
Calories to lose or gain weight
A commonly used rule of thumb is that a deficit or surplus of about 500 calories a day corresponds to roughly 0.5 kg (about 1 lb) of weight change per week, since that's a widely cited approximation of the energy stored in body fat. A smaller, "mild" adjustment of about 250 calories a day gives roughly half that rate of change. These are estimates: actual results vary by individual and change as your weight changes, so they work best as a starting point to monitor and adjust over time, not a guarantee.
Worked example
A 30-year-old woman weighing 65 kg and 165 cm tall, who is lightly active: BMR = (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1,031.25 − 150 − 161 = 1,370 kcal/day. TDEE = 1,370 × 1.375 ≈ 1,884 kcal/day. A standard weight-loss target would be about 1,384 kcal/day, and a mild target about 1,634 kcal/day.
Limitations of calorie calculators
This is an estimate based on population averages, not a measurement of your individual metabolism. It does not account for medical conditions, medications, body composition, or day-to-day variation, and it is not designed for children, pregnant or breastfeeding women, or people with eating disorders. This tool gives general estimates for information only; it is not medical or nutrition advice. If you have a medical condition or a history of disordered eating, or before starting a significant change in your diet, talk to a doctor or registered dietitian.
Real-world uses
- Getting a starting estimate of daily calorie needs for weight maintenance.
- Setting an initial calorie target when aiming to lose or gain weight gradually.
- Understanding how activity level changes daily energy needs.
- Checking calorie needs alongside your BMI as part of a general picture of weight and health.
Frequently asked questions
How many calories should I eat a day?
It depends on your age, sex, height, weight and activity level. This calculator gives an estimate of your maintenance calories (TDEE), along with adjusted targets for weight loss or gain.
What is the difference between BMR and TDEE?
BMR is the calories your body burns at complete rest. TDEE adds the calories burned through daily activity, exercise and digestion on top of BMR, and is the number most people use to plan their intake.
How many calories do I need to lose weight?
A commonly used approach is to eat around 500 calories a day below your TDEE for roughly 0.5 kg a week of loss, or about 250 calories below for a milder, roughly 0.25 kg a week pace.
Is the Mifflin-St Jeor equation accurate?
It's one of the more accurate widely used formulas for estimating BMR in the general adult population, but like any formula it's an estimate, not a direct measurement, and individual results can vary.
Why do calorie calculators give different results?
Different calculators may use different formulas (such as Harris-Benedict instead of Mifflin-St Jeor) or different activity multipliers, which changes the result. Differences of a few hundred calories between calculators are normal.
Does this calculator work for children?
No. The Mifflin-St Jeor equation is designed for adults. Children and teenagers have different, age-specific energy needs that this calculator does not cover.
What if the weight-loss number seems too low?
If a target falls below a commonly used safe minimum (around 1,200 kcal/day for women or 1,500 kcal/day for men), the calculator flags it. Consider the milder target instead, and speak with a health professional before eating significantly below these levels.
Should I eat exactly this many calories every day?
Treat the result as a starting estimate. Actual calorie needs shift as your weight, activity and age change, so it's normal to check in and adjust the target every few weeks based on real progress.