BMR CALCULATOR
✦ Calculate your Basal Metabolic Rate instantly · Pro Edition ✦
Mifflin-St Jeor Equation · Precision metrics
Use this free BMR calculator above to find out exactly how many calories your body burns at rest. Whether you're planning a weight loss diet, trying to build muscle, or simply curious about your metabolism, knowing your Basal Metabolic Rate is the first step toward setting accurate, realistic calorie goals.
What Is BMR (Basal Metabolic Rate)?
Basal Metabolic Rate, or BMR, is the number of calories your body needs to perform its most basic, life-sustaining functions while completely at rest. This includes breathing, circulating blood, maintaining body temperature, growing and repairing cells, and keeping your brain and nervous system running. Even if you spent an entire day lying in bed doing nothing, your body would still burn this baseline number of calories.
A BMR calculator like the one above uses your age, gender, height, and weight to estimate this number in seconds, saving you the time and expense of a clinical metabolic test.
Why BMR Matters for Weight Management
Your BMR typically accounts for 60 to 75 percent of the total calories you burn each day, making it the single biggest factor in your overall energy expenditure. Understanding your BMR helps you set a calorie target that supports fat loss, muscle gain, or weight maintenance without under-eating or over-eating. According to the NHS guidance on calories, balancing calorie intake with energy expenditure is central to healthy, sustainable weight management.
How Does This BMR Calculator Work?
This tool calculates your Basal Metabolic Rate instantly as you type, using a scientifically validated formula. There is no need to click a button, though a manual "Calculate" option is available if you prefer to enter all your details first.
The Mifflin-St Jeor Equation Explained
This BMR calculator is built on the Mifflin-St Jeor equation, which is widely regarded by nutrition professionals as one of the most accurate BMR formulas available for the general population. It replaced the older Harris-Benedict equation because it has been shown to more closely match results from indirect calorimetry testing. The National Center for Biotechnology Information (NCBI) hosts multiple peer-reviewed studies comparing these predictive equations for accuracy.
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) − 161
How to Use the BMR Calculator
Getting your result takes less than a minute. Follow these simple steps:
- Select your gender by tapping Male or Female at the top of the calculator.
- Enter your age in years, using the number field provided.
- Enter your height in centimeters and weight in kilograms.
- View your BMR result instantly in the result panel — it updates live as you type.
- Select an activity level from the dropdown to also see your estimated TDEE (Total Daily Energy Expenditure).
BMR vs TDEE — What's the Difference?
While BMR tells you how many calories you burn at complete rest, TDEE (Total Daily Energy Expenditure) adds in the calories you burn through daily movement, exercise, and digestion. TDEE is the number you should actually use when planning a calorie deficit for weight loss or a surplus for muscle gain.
Activity Multipliers Used to Estimate TDEE
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise, desk job | 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 |
| Extremely Active | Athlete or physically demanding job | BMR × 1.9 |
For a deeper dive into daily calorie planning, check out the TDEE Calculator on Floan, which builds directly on your BMR result.
Factors That Affect Your Basal Metabolic Rate
Several personal factors influence how high or low your BMR is compared to someone else of the same age or weight.
Age
BMR naturally declines with age, largely due to a gradual loss of muscle mass and changes in hormone levels.
Gender
Men typically have a higher BMR than women of the same age and weight because they tend to carry more lean muscle mass and less body fat.
Body Composition
Muscle tissue is metabolically more active than fat tissue, so a higher muscle-to-fat ratio raises your BMR.
Genetics and Hormones
Thyroid function and genetic factors can shift your metabolic rate up or down. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) notes that hormonal and genetic differences are a key reason BMR varies between individuals of similar size.
Tips to Support a Healthy Metabolism
- Strength train regularly to build and preserve lean muscle mass.
- Eat enough protein to support muscle repair and growth.
- Avoid extreme calorie restriction, which can cause your body to lower its BMR to conserve energy.
- Stay hydrated, since even mild dehydration can slightly reduce metabolic efficiency.
- Prioritize sleep, as poor sleep is linked to hormonal imbalances that can affect metabolism.
Once you know your BMR and TDEE, pair it with the Calorie Calculator on Floan or the BMI Calculator on Floan to build a complete picture of your health metrics.
Frequently Asked Questions
What is a good BMR score?
There is no single "good" or "bad" BMR score, since it depends on your age, height, weight, and gender. A higher BMR generally means your body burns more calories at rest, which is common in taller, more muscular individuals. Comparing your BMR to your own baseline over time is more useful than comparing it to someone else's.
How accurate is a BMR calculator?
Formula-based BMR calculators using the Mifflin-St Jeor equation are considered fairly accurate for most healthy adults, typically within about 10 percent of results from clinical indirect calorimetry testing. Individual metabolism can still vary due to genetics, muscle mass, and underlying health conditions.
What is the difference between BMR and TDEE?
BMR is the number of calories your body needs at complete rest just to stay alive. TDEE adds your activity level on top of BMR to estimate your true daily calorie needs, including exercise, walking, and everyday movement.
Should I eat below my BMR to lose weight?
Most health experts recommend not eating below your BMR for extended periods, since it can slow your metabolism and deprive your body of energy for basic functions. A safer approach for weight loss is a moderate calorie deficit below your TDEE, not your BMR.
Does muscle mass affect BMR?
Yes. Muscle tissue burns more calories at rest than fat tissue, so people with higher muscle mass typically have a higher BMR. This is one reason strength training is often recommended alongside cardio for long-term metabolic health.
Educational content only — not a substitute for professional medical advice. Consult a doctor or registered dietitian before making significant changes to your diet or exercise routine. Sources: NHS, NIDDK, NCBI.