BMR Calculator
Calculate your Basal Metabolic Rate (BMR) — the number of calories your body needs at complete rest — using the gold-standard Mifflin-St Jeor equation. See your TDEE (Total Daily Energy Expenditure) across five activity levels.
This calculator provides general estimates for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.
How It Works
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — essentially the energy required to keep your heart beating, lungs breathing, and organs functioning. It accounts for roughly 60–75% of total daily energy expenditure in sedentary individuals.
The Mifflin-St Jeor equation (1990) is considered the most accurate predictive equation for BMR in most adult populations, outperforming the older Harris-Benedict equation in studies by the Academy of Nutrition and Dietetics.
Formula:
Male: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Female: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
The difference of 166 between male and female equations reflects average hormonal and body composition differences — men typically have more lean muscle mass, which is more metabolically active than fat tissue.
To estimate Total Daily Energy Expenditure (TDEE), multiply BMR by an activity factor:
- Sedentary (little or no exercise): BMR × 1.2
- Lightly active (light exercise 1–3 days/week): BMR × 1.375
- Moderately active (moderate exercise 3–5 days/week): BMR × 1.55
- Very active (hard exercise 6–7 days/week): BMR × 1.725
- Extra active (very hard exercise, physical job): BMR × 1.9
These multipliers (sometimes called Harris-Benedict activity factors) are rough estimates. Actual TDEE varies with individual muscle mass, non-exercise activity thermogenesis (NEAT), and metabolic efficiency.
Frequently Asked Questions
What is the difference between BMR and TDEE?
BMR is the calories you burn at complete rest — your baseline metabolic cost. TDEE (Total Daily Energy Expenditure) adds in all movement: exercise, walking, fidgeting, and daily activities. To maintain body weight, you need to eat approximately TDEE calories per day. BMR is a theoretical floor; almost everyone burns significantly more.
How accurate is Mifflin-St Jeor?
Studies show Mifflin-St Jeor predicts BMR within 10% for about 82% of people. It is less accurate for the very obese (where lean mass percentage is unusually low) and for very lean athletes (where lean mass percentage is unusually high). For athletes, the Katch-McArdle formula — which uses lean body mass directly — may be more accurate.
Can I eat exactly BMR calories?
No. BMR is the calorie floor for a comatose person. Even minimal daily activity (getting up, sitting, light movement) burns significantly more. Eating at BMR would create a deficit for almost everyone. Use your TDEE as the baseline for dietary planning, and subtract 250–500 calories/day for gradual fat loss.
Does BMR change over time?
Yes. BMR declines roughly 1–2% per decade after age 20, partly due to hormonal changes and partly due to loss of muscle mass (sarcopenia). Building and maintaining muscle through resistance training is one of the most effective ways to keep BMR elevated as you age.