BMR Calculator
Calculate your Basal Metabolic Rate - calories burned at rest.
Related Calculators
About This Calculator
Ever wondered "how many calories do I burn just by existing?" That's exactly what your Basal Metabolic Rate (BMR) tells you—and the answer might surprise you.
Your BMR represents the calories your body burns doing absolutely nothing. Not sleeping-on-the-couch nothing. We mean if-you-were-in-a-coma nothing. Breathing, circulating blood, growing cells, maintaining body temperature—these "invisible" processes consume 60-75% of your daily calories. Yes, most of your calorie burn happens without you lifting a finger.
Here's the kicker: two people who weigh the same can have vastly different BMRs. A 180-pound person with lots of muscle might burn 1,900 calories at rest. Another 180-pound person with less muscle might only burn 1,500. That's a 400-calorie daily difference—or 42 pounds per year if eating the same diet.
This is why crash diets backfire. Slash calories too aggressively, and your body responds by lowering your BMR—it thinks you're starving. You lose weight initially, but your metabolism slows. When you start eating normally again, your now-slower metabolism can't keep up, and the weight piles back on (often with interest).
The Mifflin-St Jeor equation our calculator uses is the gold standard, shown to be accurate within 10% for most people in a 2024 clinical study. But remember: BMR is your starting point, not your whole story. Your actual daily calorie needs depend on how active you are—that's your TDEE (Total Daily Energy Expenditure).
How to Use the BMR Calculator
- 1**Enter your biological sex**: Men generally have higher BMRs due to greater muscle mass and testosterone. The formulas account for this difference.
- 2**Input your age**: BMR decreases approximately 1-2% per decade after age 20. This is primarily due to muscle loss—another reason to strength train as you age.
- 3**Enter your height accurately**: Taller people have higher BMRs because they have more body mass to maintain. Measure without shoes for accuracy.
- 4**Enter your current weight**: Use a consistent time (morning, before eating) for the most accurate number. Daily weight can fluctuate 2-5 lbs from water.
- 5**Optional - Enter body fat %**: If you know your body fat percentage, the calculator can use the Katch-McArdle formula, which is more accurate for lean or overweight individuals.
- 6**Review all three formulas**: We show Mifflin-St Jeor (most accurate for most people), Harris-Benedict (original), and Katch-McArdle (best if you know your body fat %).
- 7**Apply an activity multiplier**: To get your TDEE, multiply BMR by your activity level (1.2 for sedentary up to 1.9 for extremely active).
BMR Formulas Explained: Which One Should You Use?
Not all BMR formulas are created equal. Here's what the research says:
Mifflin-St Jeor Equation (Most Recommended)
Developed in 1990 and validated extensively, this is the formula recommended by the American Dietetic Association:
For Men:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5
For Women:
BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161
A 2024 clinical study found Mifflin-St Jeor matches measured BMR within 10% for 50.4% of people—better than any other formula.
Harris-Benedict Equation (Original)
Created in 1919, revised in 1984. Still widely used but tends to overestimate:
For Men:
BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) - (5.677 × age)
For Women:
BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) - (4.330 × age)
Katch-McArdle Formula (If You Know Your Body Fat %)
The most accurate formula IF you have an accurate body fat measurement:
BMR = 370 + (21.6 × lean body mass in kg)
Lean body mass = Total weight × (1 - body fat percentage as decimal)
Why it's better for athletes: A muscular person at 180 lbs with 10% body fat has 162 lbs of lean mass. A sedentary person at 180 lbs with 30% body fat has only 126 lbs of lean mass. Katch-McArdle captures this difference; the other formulas don't.
Real-World BMR Examples: What the Numbers Actually Mean
Let's calculate BMR for real-world scenarios:
Example 1: 30-Year-Old Man
- Height: 5'10" (178 cm)
- Weight: 180 lbs (82 kg)
- Mifflin-St Jeor: (10 × 82) + (6.25 × 178) - (5 × 30) + 5 = 1,787 calories
This man burns nearly 1,800 calories just existing. With moderate activity (gym 3x/week), his TDEE would be about 2,770 calories.
Example 2: 35-Year-Old Woman
- Height: 5'5" (165 cm)
- Weight: 145 lbs (66 kg)
- Mifflin-St Jeor: (10 × 66) + (6.25 × 165) - (5 × 35) - 161 = 1,366 calories
With light activity (office job, occasional walks), her TDEE would be about 1,878 calories.
Example 3: Why Body Composition Matters
Two 200-lb men, both 6'0", age 40:
| Person | Body Fat % | Lean Mass | Katch-McArdle BMR |
|---|---|---|---|
| Athlete | 15% | 170 lbs (77 kg) | 370 + (21.6 × 77) = 2,033 cal |
| Sedentary | 30% | 140 lbs (64 kg) | 370 + (21.6 × 64) = 1,752 cal |
Same weight, 281 calories/day difference. Over a year, that's a 29-pound difference if they ate identically.
What Affects Your BMR (And What You Can Actually Control)
Some factors are in your control. Others, not so much:
Factors You CAN'T Control
| Factor | Impact on BMR |
|---|---|
| Age | Decreases ~1-2% per decade after 20 |
| Biological sex | Men typically 5-10% higher than women |
| Genetics | Can account for 200-500 cal/day variation |
| Height | Taller people burn more at rest |
Factors You CAN Control
| Factor | Impact on BMR |
|---|---|
| Muscle mass | Each pound of muscle burns ~6 cal/day at rest (vs. 2 cal for fat) |
| Physical activity | Regular exercise preserves metabolically active tissue |
| Sleep quality | Poor sleep can reduce BMR by 2-8% |
| Crash dieting | Severe restriction can drop BMR 15-20% |
| Protein intake | Adequate protein supports muscle retention |
The Thermic Effect: Why What You Eat Matters
Your body burns calories digesting food (called TEF—Thermic Effect of Food):
| Food Type | Calories Burned Digesting |
|---|---|
| Protein | 20-35% of calories |
| Carbohydrates | 5-15% of calories |
| Fat | 0-5% of calories |
This is one reason high-protein diets work for weight loss—you actually burn more calories processing the same amount of food.
From BMR to Weight Loss: The Math That Actually Works
Your BMR is the foundation. Here's how to build on it:
Step 1: Calculate Your TDEE
Multiply your BMR by an activity factor:
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little exercise | 1.2 |
| Lightly active | Light exercise 1-3 days/week | 1.375 |
| Moderately active | Exercise 3-5 days/week | 1.55 |
| Very active | Hard exercise 6-7 days/week | 1.725 |
| Extremely active | Physical job + exercise | 1.9 |
Example: BMR of 1,600 × 1.55 (moderate activity) = 2,480 TDEE
Step 2: Create Your Deficit (For Weight Loss)
- Lose 0.5 lb/week: Eat 250 calories below TDEE
- Lose 1 lb/week: Eat 500 calories below TDEE (recommended max for most)
- Lose 1.5 lb/week: Eat 750 calories below TDEE (aggressive)
Warning: Never eat below your BMR for extended periods. Your body will adapt by lowering your metabolism—making future weight loss harder.
Step 3: Protect Your Metabolism
| Strategy | Why It Works |
|---|---|
| Strength training | Preserves/builds muscle while losing fat |
| Adequate protein | 0.7-1g per lb of bodyweight minimizes muscle loss |
| Moderate deficit | 500 cal deficit loses fat without triggering metabolic slowdown |
| Diet breaks | Occasional maintenance-calorie days reset hunger hormones |
| Sleep 7-9 hours | Sleep deprivation increases hunger and decreases BMR |
Common BMR Myths: What the Science Actually Says
Let's debunk some metabolism myths:
Myth 1: "Eating 6 Small Meals Boosts Metabolism"
Reality: Total calories and macros matter, not meal frequency. Whether you eat 6 small meals or 2 large ones, the thermic effect is the same if total food intake is equal. Eat on whatever schedule keeps you satisfied.
Myth 2: "My Metabolism is Broken"
Reality: Metabolic adaptation is real, but "broken" metabolisms are rare. After crash dieting, your BMR might be 10-15% lower than expected. But with proper nutrition and strength training, it can recover within months. True metabolic disorders (like hypothyroidism) affect only 5% of the population.
Myth 3: "Thin People Have Fast Metabolisms"
Reality: Larger people actually have higher BMRs—there's more body to maintain. Thin people often just eat less (consciously or unconsciously) or move more. The "fast metabolism" person who eats huge meals is probably eating less the rest of the day.
Myth 4: "After 30, Your Metabolism Crashes"
Reality: BMR decreases about 1-2% per decade, not 10-20% like many believe. The real problem is muscle loss from inactivity. Stay active and strength train, and your metabolism stays largely intact well into your 70s.
Myth 5: "Certain Foods Speed Up Metabolism Significantly"
Reality: Green tea, spicy foods, and caffeine do boost metabolism—but by only 3-8% temporarily. That's 50-100 extra calories, not the 500+ some claim. No food is a metabolism miracle.
BMR for Special Populations
Standard formulas don't work equally well for everyone:
Athletes and Very Muscular People
Use Katch-McArdle if you know your body fat percentage. Standard formulas underestimate BMR in muscular individuals by 100-300 calories.
Older Adults (65+)
A 2025 study found Harris-Benedict may actually be more accurate for older adults than Mifflin-St Jeor. BMR naturally decreases with age, but maintaining muscle through strength training can offset much of this decline.
Very Overweight Individuals
Standard formulas often overestimate BMR in obesity. Why? They assume a "normal" ratio of muscle to fat. But excess weight is mostly fat, which is metabolically inactive. Consider using Katch-McArdle with an estimated body fat percentage.
Different Ethnicities
The most common formulas were developed primarily on Caucasian populations. Research shows:
| Population | BMR Difference vs. Caucasian |
|---|---|
| South Asian | May be 5-10% lower |
| African American | May be 5% lower |
| East Asian | May be 5-10% lower |
These are averages—individual variation exists within all groups.
Pregnant Women
BMR increases during pregnancy:
- First trimester: Minimal increase (~100 cal/day)
- Second trimester: ~340 cal/day increase
- Third trimester: ~450 cal/day increase
Standard BMR calculators don't account for pregnancy. Consult a healthcare provider for personalized guidance.
How to Measure Your Actual BMR
Calculator formulas are estimates. Here's how to measure the real thing:
Clinical Methods
| Method | Accuracy | Availability | Cost |
|---|---|---|---|
| Indirect Calorimetry | Gold standard (±2-3%) | Medical facilities, some gyms | $75-300 |
| Direct Calorimetry | Most accurate | Research labs only | N/A |
| Metabolic Carts | Very accurate | Medical/research settings | $100-250 |
Indirect calorimetry measures oxygen consumption and CO2 production while you rest. It takes about 15-30 minutes and requires fasting for 12+ hours.
DIY Estimation Method
If you can't get clinical testing, try this:
- Track everything you eat for 2-3 weeks (use an app)
- Weigh yourself daily at the same time
- Calculate your average daily calories and average weight change
- Do the math: If you lost 1 lb, you were in a 500 cal/day deficit on average
This isn't BMR directly, but it gives you your actual TDEE—which is more useful for practical purposes anyway.
When Is Clinical Testing Worth It?
Consider professional BMR testing if:
- You've been dieting for years with poor results
- You suspect metabolic adaptation from past crash diets
- You're an athlete optimizing performance
- You have a medical condition affecting metabolism
- Formulas give wildly different results for you
Pro Tips
- 💡Use your BMR as a floor, not a target. Always eat above your BMR to protect your metabolism—create your calorie deficit from TDEE instead.
- 💡Recalculate your BMR every 10-15 lbs of weight change. As you lose weight, your calorie needs decrease, which is why weight loss often stalls.
- 💡Strength train 2-3 times per week to build metabolically active muscle. This is the most effective way to increase your BMR long-term.
- 💡Don't trust the "calories burned" on cardio machines—they typically overestimate by 15-30%. Use your calculated TDEE as a better guide.
- 💡If you've been dieting for months, take a 1-2 week diet break at maintenance calories. This can help reset hunger hormones and prevent metabolic slowdown.
- 💡Eat 0.7-1g of protein per pound of bodyweight daily. Protein preserves muscle during weight loss and has the highest thermic effect of all macronutrients.
- 💡Track your food for at least 2 weeks to understand your actual intake. Most people underestimate calories by 20-50%.
- 💡Move throughout the day, not just during workouts. NEAT (non-exercise activity thermogenesis) can account for 15-30% of daily calorie burn.
- 💡Get 7-9 hours of quality sleep. Sleep deprivation can reduce BMR by up to 8% and increase hunger hormones significantly.
- 💡Avoid extreme calorie restriction (more than 1,000 below TDEE). Aggressive diets cause more muscle loss and metabolic slowdown.
- 💡If formulas give wildly different results, consider getting your BMR professionally measured with indirect calorimetry.
- 💡Focus on the trend, not daily numbers. BMR-based calorie targets work over weeks, not days—daily fluctuations are normal.
Frequently Asked Questions
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest—breathing, circulation, cell repair. TDEE (Total Daily Energy Expenditure) includes BMR plus all your daily activities: walking, working, exercising. For weight loss, you create a deficit from TDEE, not BMR. Your BMR might be 1,500 calories, but your TDEE could be 2,200 if you're moderately active. Always eat above your BMR but below your TDEE for healthy, sustainable weight loss.
