BMR Calculator
Calculate your basal metabolic rate and daily resting calorie burn with our free BMR calculator. Accurately estimate your baseline energy expenditure with the Mifflin-St Jeor and Katch-McArdle equations.
Basal Metabolic Rate (BMR) Explained
Basal Metabolic Rate (BMR) is the minimum number of calories your body requires to perform basic life-sustaining functions at rest. This includes breathing, circulating blood, cellular production, nutrient processing, and temperature regulation.
BMR accounts for approximately 60% to 75% of your total daily calorie burn. Using an accurate basal metabolic rate calculator gives you the scientific foundation for any nutrition plan. Closely related to a resting metabolic rate calculator (RMR), your BMR represents your baseline before physical activity. Understanding BMR and TDEE allows you to calculate an effective, healthy calorie deficit without triggering metabolic slowdown.
Our tool supports both the Mifflin-St Jeor formula (ideal for general populations) and the Katch-McArdle formula (which incorporates lean body mass from your body fat percentage for athletes). Because muscle tissue requires more energy than fat tissue at rest, increasing your lean mass will elevate your BMR over time.
Knowing your BMR helps you determine your metabolic baseline. You should never consume fewer calories than your BMR for extended periods unless under strict medical supervision, as doing so can trigger metabolic slowdown, nutrient deficiencies, and muscle loss.
About this Calculator
Methodology & Formulas: This Bmr calculator uses standard physiological formulas and evidence-based guidelines to provide accurate estimates.
Reviewed by: Dr. Rekha Kumar, M.D., M.S., Lead Medical Reviewer
Last Updated: August 2026
Sources & Citations: Guidelines from the NIH and CDC were consulted in the creation of this tool.
Disclaimer: This tool is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider.
Frequently Asked Questions
Q: What is the difference between a BMR calculator and a resting metabolic rate calculator?
While often used interchangeably, a basal metabolic rate calculator measures energy expenditure under strict fasting, post-sleep resting conditions. A resting metabolic rate calculator (RMR) measures resting calorie burn under slightly less restrictive conditions and is typically about 5% to 10% higher than BMR.
Q: How do BMR and TDEE work together for weight loss?
Your BMR is the baseline calories needed for vital organ function at rest. Your Total Daily Energy Expenditure (TDEE) multiplies BMR by your physical activity level. To lose weight safely, consume fewer calories than your TDEE, but never drop below your BMR for extended periods.
Q: What is BMR?
BMR stands for Basal Metabolic Rate, representing the energy your body expends just to stay alive at rest, without any activity or food digestion factored in.
Q: Does eating below BMR damage metabolism?
Consuming calories below your BMR for too long can cause adaptive thermogenesis (metabolic slowdown) where your body conserves energy and burns muscle for fuel.
Scientific References & Clinical Guidelines
- CDC Healthy Weight Guidelines - Centers for Disease Control and Prevention
- NIH National Heart, Lung, and Blood Institute (NHLBI) Obesity Guidelines
- PubMed studies on rate of fat mass vs. lean mass loss