BMR calculator
Estimate basal metabolic rate (BMR)—the energy your body needs at full rest for organs, breathing, and temperature—using the Mifflin–St Jeor formula. We also show example daily totals when you multiply BMR by common activity factors (those numbers approximate TDEE tiers). This is for education, not a clinical test. Your inputs stay on this device.
What is BMR?
BMR is the energy required to keep basic physiology running if you were resting in a controlled setting. It does not include digestion, fidgeting, or exercise—those are captured when you move to TDEE using activity multipliers (the row of numbers above) or a dedicated TDEE calculator.
Mifflin–St Jeor is one of several published estimates; it tends to perform well in modern populations, but your measured resting metabolism can still differ because of muscle mass, thyroid function, and genetics.
What to do with this number
- Compare BMR to TDEE when explaining why “I barely move” still burns more than bed rest.
- Do not slash calories to BMR without medical oversight—most adults need more for daily life.
- Re-run when weight changes a lot, since BMR is partially tied to lean mass and body size.
Common mistakes
- Confusing BMR with the calories you “should” eat (activity and goals matter).
- Ignoring that menstrual cycle, sleep debt, and illness can shift real burn without changing the formula.
- Using kcal from one equation while logging food in another app that uses a different BMR model.
Frequently asked questions
What equation does this BMR calculator use?
Mifflin–St Jeor, with the standard +5 (male) or −161 (female) term.
Is BMR the same as calories I should eat?
No. It is a floor for resting metabolism. Total intake targets usually start from TDEE or clinical advice.
Medical disclaimer: Educational only. For personalized nutrition or medical nutrition therapy, consult a qualified professional.