Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using scientifically validated formulas. Discover how many calories your body burns at rest.
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Basal Metabolic Rate (BMR) is the number of calories your body needs to perform essential physiological functions while at complete rest. These functions include:
BMR represents approximately 60-75% of your total daily energy expenditure, making it the largest component of calorie burn for most people.
There are three widely-used scientific formulas for calculating BMR:
Developed in 1990, this is currently considered the most accurate formula for most people.
Originally created in 1919 and revised in 1984. Still widely used and fairly accurate.
Takes lean body mass into account. More accurate for people who know their body fat percentage, especially athletes with higher muscle mass.
Let's calculate BMR for a 30-year-old male who weighs 180 lbs (81.6 kg) and is 5'10" (178 cm):
| Term | Definition | Measurement Conditions |
|---|---|---|
| BMR | Basal Metabolic Rate - calories burned for essential functions | Measured in lab after 12-hour fast, lying down, complete rest |
| RMR | Resting Metabolic Rate - similar to BMR but slightly higher | Less restrictive conditions, typically 10-20% higher than BMR |
| TDEE | Total Daily Energy Expenditure - total calories burned per day | BMR + activity + digestion + thermogenesis |
To determine your total daily calorie needs, multiply your BMR by an activity factor:
Muscle tissue burns more calories at rest than fat tissue. People with higher muscle mass have higher BMRs. This is why strength training can boost your metabolism even when you're not exercising.
BMR decreases by about 1-2% per decade after age 20. This is primarily due to loss of muscle mass (sarcopenia) and hormonal changes. Maintaining muscle through resistance training can help counteract this decline.
Men typically have 5-10% higher BMRs than women due to higher muscle mass and lower body fat percentage. This difference is reflected in the gender-specific formulas used to calculate BMR.
Genetic factors can cause BMR to vary by up to 26% between individuals, even with similar body composition. Some people are naturally "fast burners" while others have slower metabolisms.
Living in extreme temperatures (very hot or cold climates) can increase BMR by 5-20% as your body works harder to maintain core temperature through thermoregulation.
Thyroid hormones significantly impact BMR. Hyperthyroidism (overactive thyroid) increases BMR, while hypothyroidism (underactive thyroid) decreases it. Pregnancy and menstrual cycle also affect metabolism.
Consuming fewer calories than your BMR can slow metabolism, cause muscle loss, and lead to nutrient deficiencies. Always aim to eat between your BMR and TDEE for healthy, sustainable weight loss.
Muscle tissue burns about 6 calories per pound per day at rest, compared to 2 calories per pound for fat tissue. Adding 10 pounds of muscle could increase your BMR by 40-60 calories per day.
Drinking water can temporarily boost metabolism by 10-30% for about an hour. Aim for 8-10 glasses of water per day. Cold water may have a slightly greater effect as your body uses energy to warm it to body temperature.
Protein has the highest thermic effect of food (TEF) - your body burns 20-30% of protein calories during digestion, compared to 5-10% for carbs and 0-3% for fats. Aim for 0.8-1.2g of protein per pound of body weight.
Poor sleep disrupts hormones that regulate metabolism (leptin and ghrelin), potentially reducing BMR. Aim for 7-9 hours of quality sleep per night to maintain optimal metabolic function.
Severe calorie restriction (eating well below BMR) can decrease your metabolic rate by up to 23%. Your body enters "starvation mode" to conserve energy. Maintain a moderate deficit and eat at least your BMR calories.
No, but they're very similar. BMR is measured under very strict laboratory conditions (after 12-hour fast, complete rest). RMR is measured under less restrictive conditions and is typically 10-20% higher than BMR. For practical purposes, most calculators (including this one) estimate RMR and call it BMR.
The Mifflin-St Jeor formula is currently considered most accurate for the general population. The Katch-McArdle formula is more accurate for athletes or individuals with known body fat percentage. Studies show Mifflin-St Jeor is accurate within ±10% for most people.
Eat based on your TDEE (not BMR) according to your goals: For weight loss, eat 10-20% below TDEE; for maintenance, eat at TDEE; for muscle gain, eat 10-20% above TDEE. Never eat below your BMR for extended periods.
BMR varies based on age, gender, body composition, height, weight, and genetics. A taller, heavier, more muscular, younger male will have a significantly higher BMR than a shorter, lighter, less muscular, older female. Genetic variations can also cause 26% variance between individuals.
Online calculators provide estimates within ±10-15% accuracy for most people. For exact measurements, you'd need indirect calorimetry testing in a lab. However, these formulas are scientifically validated and accurate enough for diet and fitness planning.
Yes, slightly. BMR is typically lowest during sleep and increases during waking hours due to increased neural activity and muscle tone. However, these variations are small (±5-10%) and the daily average remains constant unless body composition or other factors change.
Building muscle is the most effective way to increase BMR long-term. You can realistically gain 1-2 pounds of muscle per month with consistent strength training and proper nutrition. Each pound of muscle adds about 6 calories/day to your BMR. Other factors (hydration, protein intake) provide temporary boosts.
Short-term fasting (16-24 hours) actually slightly increases BMR due to adrenaline and noradrenaline release. However, prolonged fasting or severe calorie restriction for multiple days can decrease BMR. Intermittent fasting protocols done correctly don't harm metabolism.
While foods like caffeine, green tea, and spicy peppers can temporarily boost metabolism by 3-11%, the effect is modest and temporary. The thermic effect of food (TEF) varies: protein (20-30%), carbs (5-10%), and fats (0-3%). Focus on overall diet quality rather than specific "metabolism-boosting" foods.
Yes. Thyroid disorders have the most significant impact: hyperthyroidism can increase BMR by 50-100%, while hypothyroidism can decrease it by 30-40%. Other conditions affecting BMR include diabetes, Cushing's syndrome, PCOS, and chronic stress. Consult a doctor if you suspect a medical issue affecting your metabolism.