How many calories does your body burn?
Even at complete rest your body uses energy to breathe, pump blood, keep warm and run your brain: that is your basal metabolic rate (BMR). Add the activity of your day and you get your total daily energy expenditure (TDEE), the number of calories that keeps your weight stable. This calculator estimates both and suggests intakes for steady weight loss or a lean gain.
These figures are general estimates. If you have a medical condition, are pregnant, take medication that affects weight or plan a large weight loss, talk to your doctor or a registered dietitian.
The Mifflin-St Jeor equation
- Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
The calculator converts pounds and inches for you. TDEE is then BMR multiplied by an activity factor, from 1.2 for a desk job with no exercise to 1.9 for a physical job plus hard training.
Worked example: a 35-year-old man, 180 lb, 5 ft 10 in
- Weight: 180 lb = 81.6 kg, so 10 × 81.6 = 816.5.
- Height: 70 in = 177.8 cm, so 6.25 × 177.8 = 1,111.3.
- Age: 5 × 35 = 175.
- BMR: 816.5 + 1,111.3 − 175 + 5 ≈ 1,758 kcal a day.
- Lightly active (factor 1.375): 1,758 × 1.375 ≈ 2,417 kcal a day to maintain weight.
- To lose about 1 lb a week: roughly 1,917 kcal a day.
Calories by activity level (same person)
| Activity | Factor | Maintain | Lose ~1 lb/week | Lean gain |
|---|---|---|---|---|
| Sedentary | 1.2 | 2,109 | 1,609 | 2,409 |
| Lightly active | 1.375 | 2,417 | 1,917 | 2,717 |
| Moderately active | 1.55 | 2,724 | 2,224 | 3,024 |
| Very active | 1.725 | 3,032 | 2,532 | 3,332 |
| Extra active | 1.9 | 3,340 | 2,840 | 3,640 |
Using the numbers well
- Pick your activity level honestly: most people overestimate how much they burn exercising. If unsure, choose the lower factor.
- Weigh yourself under the same conditions once a week and adjust intake by 100–200 calories if the trend does not match your goal after two to three weeks.
- Keep the deficit moderate: beyond 500–750 calories a day, muscle loss, fatigue and rebound weight gain become more likely. The calculator never suggests going below 1,500 kcal for men or 1,200 kcal for women.
- Prioritize protein and strength training during weight loss to preserve muscle.
Why your metabolism differs from someone else’s
BMR rises with muscle mass and falls with age, by about 5 calories a year in the equation. Two people with the same weight can burn different amounts depending on body composition, genetics, sleep and thyroid function. Fitness trackers also estimate energy expenditure, usually with a similar margin of error, so use any number as a starting point and adjust from real-world results.