BMR Calculator
Find out how many calories your body burns just existing—before any activity.
BMR Calculator
Your Basal Metabolic Rate (BMR)
1,618 calories/day
Based on the Mifflin-St Jeor formula
BMR by Different Formulas
Mifflin-St Jeor
1,618 cal
Most accurate for general population
Harris-Benedict
1,672 cal
Classic formula (1919, revised 1984)
Katch-McArdle
1,580 cal
Best when body fat % is known
Calories Burned by Activity Level
Sleep
64 cal/hr
Sleeping, resting in bed
Sedentary
88 cal/hr
Sitting, reading, watching TV
Light
168 cal/hr
Walking slowly, light chores
Moderate
337 cal/hr
Fast walking, cycling, dancing
Intense
539 cal/hr
Running, HIIT, sports
What Does Your BMR Mean?
Your BMR of 1,618 calories represents the minimum energy your body needs to function at rest. This includes breathing, circulation, cell production, and maintaining body temperature.
Important: BMR alone doesn't account for the calories you need for daily activities. To determine your total daily energy needs (TDEE), you must factor in your activity level.
Note: These calculations provide estimates based on standard formulas and may vary based on individual factors. Consult with a healthcare professional or registered dietitian for personalized advice.
What is BMR?
BMR (Basal Metabolic Rate) is the number of calories your body burns just to keep you alive—breathing, pumping blood, making new cells, keeping your organs running. It's what you'd burn if you literally did nothing but lie in bed all day.
Your BMR makes up about 60-70% of all the calories you burn daily, which is why it matters. The rest comes from moving around and digesting food. Unlike TDEE, your BMR stays pretty constant throughout the day—it's your baseline.
Factors Affecting Your BMR
Factors That Increase BMR
- Greater muscle mass
- Regular exercise (particularly strength training)
- Taller height
- Male biological sex (typically)
- Younger age (metabolism slows with age)
- Stress and anxiety
- Pregnancy
- Fever or illness
- Certain medications (e.g., caffeine, nicotine)
- Thyroid disorders (hyperthyroidism)
Factors That Decrease BMR
- Higher body fat percentage
- Severe calorie restriction (metabolic adaptation)
- Aging
- Dehydration
- Poor sleep quality
- Thyroid disorders (hypothyroidism)
- Malnutrition
- Loss of muscle mass
- Female biological sex (typically)
- Extreme dieting history ("yo-yo dieting")
Why BMR Matters for Health
Understanding your BMR provides valuable insights into your body's energy needs and can help with:
Weight Management
BMR forms the foundation of your calorie needs. Knowing this baseline helps create appropriate calorie targets for weight loss, maintenance, or gain.
Metabolic Health
An abnormally high or low BMR may indicate underlying health issues such as thyroid dysfunction, which can be addressed with proper medical care.
Body Composition
Building and maintaining muscle mass helps support a higher BMR, contributing to better metabolic health and body composition over time.
Which Formula to Use
The calculator offers three different formulas. For most people, Mifflin-St Jeor is the most accurate—it's based on newer research and works well for the general population. If you know your body fat percentage and you're pretty lean or muscular, Katch-McArdle might be better. Harris-Benedict is the oldest formula and tends to run a bit high, but it's still used in some contexts.
Bottom line: If you're not sure which to use, go with Mifflin-St Jeor.
Can You Change Your BMR?
Not really—at least not dramatically. Your BMR is mostly set by your age, sex, and body size. But there are a few things that can nudge it up slightly:
- Build muscle: Muscle burns more calories at rest than fat does. Lift weights 2-3 times a week and eat enough protein.
- Don't crash diet: Extreme calorie restriction makes your body slow down its metabolism to conserve energy. Eat enough to support your basic needs.
- Stay hydrated and sleep well: Dehydration and poor sleep can temporarily lower your BMR.
- Keep moving as you age: Your BMR naturally drops as you get older, mostly because people lose muscle. Staying active helps slow that down.
Realistically, you might increase your BMR by 5-10% through significant muscle gain, but that takes months or years. For weight management, it's usually easier to focus on your total activity level (TDEE) rather than trying to dramatically boost your BMR.
Common Questions
What's the difference between BMR and RMR?
Technically, BMR is measured under super strict conditions—fasting, lying down, in a controlled environment. RMR (Resting Metabolic Rate) is measured under more normal conditions and is usually about 10% higher. Most people use the terms interchangeably, and for practical purposes, they're close enough.
Is a higher BMR better for weight loss?
A higher BMR means you burn more calories just existing, which can make weight management a bit easier. But there's no "good" or "bad" BMR—it's just your body. Building muscle through weight training is one of the few ways to raise it slightly, but honestly, it's easier to focus on your overall activity level than to try to dramatically boost your BMR.
Can I increase my BMR significantly?
Not dramatically, no. You might increase it 5-10% through building a lot of muscle, but that takes months or years of consistent training. Avoid crash dieting (which can actually lower it), stay hydrated, sleep well, and lift weights—those are your best bets.
Does metabolism really slow with age?
Yes, but not as much as people think. Your BMR drops about 1-2% per decade after 20, mostly because people lose muscle as they age. The good news is that staying active and lifting weights can fight this decline. A lot of what we blame on "slowing metabolism" is actually just moving less.
How accurate are BMR calculators?
Usually within 10-15% for most people, which is pretty good for an estimate. The Mifflin-St Jeor formula is the most accurate for the general population. The only way to get a truly precise measurement is expensive lab testing (calorimetry), which most people don't need anyway.
Related Calculators
Disclaimer: This BMR calculator provides estimates based on mathematical formulas and should not be considered medical advice. These calculations may not be accurate for everyone, particularly individuals with certain medical conditions or those outside typical body composition ranges. Consult with healthcare professionals before making significant changes to your diet or exercise routine.