A BMR calculator estimates how many calories your body burns at rest. It's the baseline used to calculate TDEE. Pair BMR with food tracking for effective weight management.
Quick Answer
- • BMR calculator: Estimates calories burned at rest (baseline metabolism)
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- • What's next: Calculate TDEE and scan meals
Last updated: 2026
How Many Calories Does Your Body Burn at Rest?
Calculate your Basal Metabolic Rate (BMR) — the number of calories you burn just staying alive. Essential for accurate weight loss planning.
BMR Calculator
Calculate your Basal Metabolic Rate
Frequently Asked Questions
What is BMR?
BMR (Basal Metabolic Rate) is the number of calories your body burns at rest to maintain basic physiological functions like breathing, circulation, and cell production. It represents your minimum daily energy requirement.
How is BMR calculated?
BMR is typically calculated using the Mifflin-St Jeor equation, which considers your weight, height, age, and gender. Men generally have higher BMR than women due to greater muscle mass.
Why is BMR important?
Knowing your BMR helps you understand your baseline calorie needs. This is essential for creating effective weight loss, weight gain, or maintenance nutrition plans.
What Is BMR? Basal Metabolic Rate Explained
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to stay alive. Even if you lay in bed all day, your body needs energy for:
- Breathing — respiratory muscles and gas exchange
- Circulation — your heart pumping blood 24/7
- Cell repair and production — constant tissue turnover
- Brain function — the brain uses about 20% of resting energy
- Body temperature regulation — maintaining 98.6°F (37°C)
- Organ function — liver, kidneys, and digestive system at baseline
BMR typically accounts for 60 to 70 percent of your total daily calorie burn. The remaining 30 to 40 percent comes from physical activity and the thermic effect of food (calories burned digesting what you eat).
BMR vs RMR vs TDEE: What's the Difference?
These three terms are often confused. Here is a clear comparison:
| Term | Full Name | What It Means | How to Use It |
|---|---|---|---|
| BMR | Basal Metabolic Rate | Calories burned at complete rest (bed rest) | Baseline; the floor of your calorie needs |
| RMR | Resting Metabolic Rate | Calories burned at rest (not strictly bed rest) | Similar to BMR; measured under less strict conditions |
| TDEE | Total Daily Energy Expenditure | BMR + activity + digestion (TEF) | What you actually burn in a day; use for calorie targets |
BMR and RMR are nearly identical in practice (RMR is measured under slightly less strict conditions). Both represent your resting calorie floor. TDEE is what you actually burn in a day and is the number you use to set calorie targets.
The 3 BMR Formulas: Full Equations and Comparison
Three formulas are commonly used to estimate BMR. All use weight (w) in kg, height (h) in cm, and age (a) in years. Katch-McArdle uses lean body mass (LBM) instead of total weight.
Mifflin-St Jeor
Men: BMR = 10w + 6.25h − 5a + 5
Women: BMR = 10w + 6.25h − 5a − 161
Most accurate for general population; uses weight, height, age
Harris-Benedict
Men: BMR = 66.47 + 13.75w + 5.003h − 6.755a
Women: BMR = 655.1 + 9.563w + 1.85h − 4.676a
Original 1919 formula; slightly overestimates BMR
Katch-McArdle
Both: BMR = 370 + 21.6 × LBM(kg)
Most accurate if you know body fat %; uses lean body mass
Sources: Mifflin-St Jeor (1990); Harris-Benedict (1919, revised 1984); Katch-McArdle (leverages lean body mass). The Academy of Nutrition and Dietetics recommends Mifflin-St Jeor as the most accurate for the general population.
Worked Example: 30-Year-Old Man, 80 kg, 178 cm
Here is the full BMR calculation using the Mifflin-St Jeor equation step by step.
Step 1 — Apply the men's Mifflin-St Jeor formula:
BMR = 10 × w + 6.25 × h − 5 × a + 5
Step 2 — Plug in the values (w = 80, h = 178, a = 30):
BMR = 10 × 80 + 6.25 × 178 − 5 × 30 + 5
Step 3 — Solve each term:
BMR = 800 + 1,112.5 − 150 + 5
BMR = 1,767.5 ≈ 1,768 cal/day
This man burns about 1,768 calories per day at complete rest. To find his actual daily burn (TDEE), multiply by an activity factor — see the next section.
What Affects Your BMR: 5 Key Factors
Age
BMR declines about 1 to 2 percent per decade after age 20, primarily due to natural muscle loss (sarcopenia). Staying active and strength training slows this decline.
Sex
Men typically have a higher BMR than women of the same size because they carry more muscle mass and less body fat on average.
Muscle Mass
Muscle is metabolically active tissue. Each pound of muscle burns roughly 6 to 10 calories per day at rest, versus about 2 calories per pound of fat. More muscle means a higher BMR.
Genetics
Some people inherit a naturally higher or lower metabolic rate. Genetic variation in thyroid function and muscle fiber type can shift BMR by 5 to 10 percent.
Hormones
Thyroid hormones (T3 and T4) directly regulate metabolic rate. An underactive thyroid (hypothyroidism) can lower BMR by 10 to 20 percent. Stress hormones and sex hormones also play a role.
How to Use Your BMR: Multiply by Activity to Get TDEE
BMR is just the starting point. To find how many calories you actually burn in a day, multiply your BMR by an activity factor. The result is your TDEE — the number you use to set calorie targets for weight loss, maintenance, or muscle gain.
TDEE = BMR × Activity Factor
| Activity Level | Multiplier |
|---|---|
| Sedentary (desk job, little exercise) | 1.2 |
| Lightly active (1–3 days/week) | 1.375 |
| Moderately active (3–5 days/week) | 1.55 |
| Very active (6–7 days/week) | 1.725 |
| Extra active (physical job + training) | 1.9 |
For our 1,768-calorie BMR example with a moderate activity level (1.55): TDEE = 1,768 × 1.55 = 2,740 calories per day. Use the TDEE Calculator to get your full daily burn automatically.
Can You Increase Your BMR? An Honest Answer
Yes, but not by much, and not with "metabolism boosters." Here is what actually works and what does not:
- Build muscle (works): Adding 10 pounds of muscle raises BMR by roughly 60 to 100 calories per day. This is the single most effective strategy. Resistance train 2 to 4 times per week.
- Increase NEAT (works): Non-exercise activity thermogenesis — walking, standing, fidgeting — can add 100 to 500 calories per day to your total burn. Aim for 8,000 to 10,000 steps.
- Eat enough protein (helps): Protein has a higher thermic effect (20 to 30 percent) than carbs (5 to 10 percent) or fat (0 to 3 percent). A high-protein diet modestly increases the calories you burn digesting food.
- Avoid crash diets (prevents decline): Very low-calorie diets can lower BMR by up to 20 percent through metabolic adaptation. Eat at a moderate deficit and take diet breaks.
- "Metabolism boosters" (do not work): Green tea extract, cayenne pills, and similar supplements have a negligible effect — typically less than 50 to 100 calories per day, and the effect fades.
The honest truth: you cannot dramatically increase BMR with supplements or tricks. Building muscle and staying active are the only proven, lasting methods.
BMR Calculator FAQs
Disclaimer: This BMR calculator provides estimates for educational purposes only and is not medical advice. The Mifflin-St Jeor equation has a standard error of about plus or minus 10 percent. Individual metabolic rates vary based on genetics, hormones, and body composition. Consult a healthcare professional before making significant dietary changes, especially if you have a medical condition.
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