BMR and TDEE in plain words
Your basal metabolic rate (BMR) is the energy your body uses at complete rest: breathing, keeping warm, running your organs. Your total daily energy expenditure (TDEE) adds everything else: walking, working, exercising and digesting food. If you eat about as many calories as your TDEE, your weight stays roughly stable.
The formula: Mifflin-St Jeor
Several equations estimate BMR. The Mifflin-St Jeor equation, published in 1990, is the one many dietitians use today because studies found it the most accurate of the common equations for healthy adults.
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
TDEE = BMR × activity factor
| Activity level | Factor |
|---|---|
| Sedentary (little or no exercise) | 1.2 |
| Lightly active (1–3 days a week) | 1.375 |
| Moderately active (3–5 days a week) | 1.55 |
| Very active (6–7 days a week) | 1.725 |
| Extra active (physical job plus training) | 1.9 |
Worked examples
A moderately active man
30 years old, 80 kg, 180 cm. BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal. Exercising 3–5 days a week: TDEE = 1,780 × 1.55 = 2,759 kcal per day.
A lightly active woman
30 years old, 60 kg, 165 cm. BMR = 600 + 1,031.25 − 150 − 161 = 1,320 kcal. Lightly active: TDEE = 1,320 × 1.375 ≈ 1,815 kcal per day.
Calories to lose or gain weight
A pound of body fat stores roughly 3,500 kcal (about 7,700 kcal per kilogram), which gives the classic rule of thumb: eating about 500 kcal less than your TDEE each day leads to roughly 0.5 kg (1 lb) of weight loss per week at first. In reality weight loss slows over time, because a smaller body burns less energy and the body adapts, so treat this as a starting point and adjust every few weeks based on your actual progress.
- Maintain: eat around your TDEE.
- Lose weight steadily: TDEE minus 300–500 kcal.
- Gain weight or muscle: TDEE plus 250–500 kcal, together with strength training.
Very low intakes are hard to sustain and make it difficult to get enough protein, vitamins and minerals. Many health services advise not going below about 1,200 kcal a day for women and 1,500 kcal for men without medical supervision, and the calculator will not suggest less.
How accurate is this?
For most people, Mifflin-St Jeor predicts resting energy use within about 10%. Errors are larger for very muscular people (who burn more than predicted), for people with obesity, and in older age. The activity factor adds more uncertainty, because most of us overestimate how active we are. If you are unsure, choose the lower level.
The best way to find your real maintenance calories is to track your intake and weight for two to three weeks. If your weight is stable, your average intake is your TDEE.
Common mistakes
- Counting exercise twice: choosing a high activity level and then also "eating back" the calories shown on a fitness tracker.
- Weighing yourself only once a week: daily weight swings by 1–2 kg because of water and food. Use a weekly average.
- Cutting too hard: a 1,000 kcal deficit may look faster, but it is harder to keep up and costs more muscle.
These numbers are estimates for healthy adults. Pregnancy, breastfeeding, medical conditions and some medicines change energy needs; ask a doctor or registered dietitian for personal advice.
Frequently asked questions
How many calories should I eat a day?
About as many as your TDEE to maintain your weight. The Dietary Guidelines for Americans estimate roughly 1,600–2,400 kcal for adult women and 2,000–3,000 kcal for adult men, but your own number depends on size, age and activity.
What is the difference between BMR and TDEE?
BMR is the energy you burn at complete rest. TDEE is BMR plus everything you do during the day, so it is always higher.
How many calories should I cut to lose 1 lb a week?
About 500 kcal per day below your TDEE, as a starting point. Progress usually slows over time, so review every few weeks.
Which activity level should I choose?
Count only planned exercise sessions and physical work. If you are unsure between two levels, choose the lower one.
Is Mifflin-St Jeor better than Harris-Benedict?
Studies comparing the equations found Mifflin-St Jeor more often within 10% of measured resting energy use in healthy adults, which is why many dietitians prefer it.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990; 51: 241–247.
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association, 2005; 105: 775–789.
- Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet, 2011; 378: 826–837.
- U.S. Department of Agriculture and HHS. Dietary Guidelines for Americans 2020–2025, Appendix 2: Estimated Calorie Needs.
Last reviewed 5 October 2026. Results are estimates; see our disclaimer.