Key Takeaways
- BMR is the minimum calories your body needs at complete rest
- BMR accounts for 60-75% of your total daily calorie burn
- Muscle mass increases BMR - strength training can boost metabolism
- Safe weight loss requires a deficit of 500-1000 calories/day
- Never eat below your BMR - it can slow metabolism and harm health
What Is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain vital functions like breathing, circulation, cell production, and body temperature regulation. Think of it as the energy cost of simply being alive - even if you stayed in bed all day, your body would still burn this many calories.
Your BMR is influenced by several factors including age, gender, height, weight, and body composition. Men typically have higher BMRs than women due to greater muscle mass, and BMR naturally decreases with age as we lose lean muscle tissue.
The Harris-Benedict BMR Formula
Our calculator uses the revised Harris-Benedict equation, one of the most accurate and widely-used formulas for estimating BMR:
Men: BMR = 88.36 + (13.4 x weight in kg) + (4.8 x height in cm) - (5.7 x age)
Women: BMR = 447.6 + (9.2 x weight in kg) + (3.1 x height in cm) - (4.3 x age)
How to Use This BMR Calculator
Enter Your Age
Input your current age in years. BMR decreases by about 1-2% per decade after age 20.
Enter Your Weight and Height
Provide your weight in pounds and height in feet and inches for accurate calculations.
Select Your Gender
Men typically have 10-15% higher BMR than women of the same weight due to higher muscle mass.
Choose Activity Level and Goal
Select how active you are to calculate TDEE, then choose your weight goal to get target calories.
BMR vs. TDEE: What's the Difference?
BMR represents your resting calorie burn, while TDEE (Total Daily Energy Expenditure) includes all activities throughout the day. TDEE is calculated by multiplying your BMR by an activity factor:
- Sedentary: BMR x 1.2 (desk job, little exercise)
- Lightly Active: BMR x 1.375 (light exercise 1-3 days/week)
- Moderately Active: BMR x 1.55 (moderate exercise 3-5 days/week)
- Active: BMR x 1.725 (hard exercise 6-7 days/week)
- Very Active: BMR x 1.9 (very hard exercise, physical job)
Pro Tip: Never Eat Below Your BMR
While you want a calorie deficit for weight loss, eating below your BMR can trigger your body's starvation response, slowing your metabolism and making weight loss harder. Aim for your target calories to be at least equal to your BMR for sustainable results.
Using BMR for Weight Management
Understanding your BMR and TDEE is crucial for effective weight management:
For Weight Loss
Create a calorie deficit by eating 500-1000 calories below your TDEE. A 500-calorie daily deficit results in approximately 1 pound of weight loss per week, while 1000 calories yields about 2 pounds. Never go below your BMR, as this can harm your metabolism.
For Weight Maintenance
Eat at your TDEE level. If you're maintaining weight, you've found your caloric balance. Adjust based on weekly weight trends - if you're gaining, reduce by 100-200 calories; if losing, increase slightly.
For Weight Gain
Eat 500-1000 calories above your TDEE for healthy weight gain. Combined with strength training, this surplus supports muscle growth. Aim for 0.5-1 pound of gain per week to minimize fat accumulation.
How to Boost Your BMR
- Build Muscle: Each pound of muscle burns about 6 calories at rest daily, compared to 2 for fat
- Eat Enough Protein: Protein has a higher thermic effect, burning more calories during digestion
- Stay Active: Regular exercise temporarily boosts metabolism for hours after your workout
- Get Enough Sleep: Sleep deprivation can reduce BMR by 2-8%
- Stay Hydrated: Proper hydration supports optimal metabolic function
Frequently Asked Questions
A "normal" BMR varies widely based on age, gender, weight, and height. For adult men, BMR typically ranges from 1,600-1,800 calories/day, while women average 1,400-1,600 calories/day. Athletes and those with more muscle mass often have higher BMRs.
BMR decreases approximately 1-2% per decade after age 20, primarily due to loss of lean muscle mass (sarcopenia). Regular strength training can help preserve muscle and maintain a higher BMR as you age.
BMR is a component of your total metabolism. Your complete daily calorie burn (metabolism) includes BMR plus the thermic effect of food (digestion), physical activity, and non-exercise activity thermogenesis (NEAT). BMR represents the largest portion - typically 60-75% of total daily calories burned.
Yes, severe calorie restriction can trigger "metabolic adaptation" where your body reduces BMR to conserve energy. This is why crash diets often fail long-term. Aim for a moderate deficit (500-1000 calories below TDEE) and never eat below your BMR to avoid this effect.
The Harris-Benedict equation used here is accurate within about 10% for most people. For the most precise measurement, indirect calorimetry testing at a medical facility is required. Use this calculator as a starting point and adjust based on your actual weight changes over time.