Basal Metabolic Rate (BMR) Calculator
The Basal Metabolic Rate (BMR) Calculator estimates the energy expended while at rest in a neutrally temperate environment, in a post-absorptive state (after ~12 hours of fasting).
Calculate Your BMR
What is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions. These functions include breathing, circulation, cell production, nutrient processing, protein synthesis, and ion transport. Essentially, your BMR is the amount of energy expended while at rest in a neutrally temperate environment, in the post-absorptive state (meaning that the digestive system is inactive, which requires about 12 hours of fasting).
How is BMR Calculated?
There are several formulas used to calculate BMR. The most commonly used are the Mifflin-St Jeor Equation and the Harris-Benedict Equation. Our calculator uses the Mifflin-St Jeor Equation, which is considered more accurate than the Harris-Benedict formula.
Mifflin-St Jeor Equation:
- For men: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(y) + 5
- For women: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age(y) - 161
Harris-Benedict Equation (Revised):
- For men: BMR = 13.397 × weight(kg) + 4.799 × height(cm) - 5.677 × age(y) + 88.362
- For women: BMR = 9.247 × weight(kg) + 3.098 × height(cm) - 4.330 × age(y) + 447.593
Factors That Affect BMR
Several factors can influence your Basal Metabolic Rate:
- Body size and composition: Larger bodies and more muscle mass typically result in a higher BMR.
- Age: Metabolism slows with age due to loss of muscle tissue.
- Gender: Men typically have a higher BMR than women due to greater muscle mass.
- Genetics: Some people are born with a faster metabolism than others.
- Thyroid function: The thyroid gland regulates metabolism, and imbalances can affect BMR.
- Climate: People in colder climates may have a slightly higher BMR.
- Diet: Severe calorie restriction can lower BMR.
- Exercise: Regular exercise, especially strength training, can increase BMR.
Why is Knowing Your BMR Important?
Understanding your BMR can help you make informed decisions about your diet and exercise regimen. It provides a baseline for determining how many calories you need to maintain, lose, or gain weight. By knowing your BMR, you can:
- Create a personalized calorie budget for weight management
- Set realistic weight loss or gain goals
- Understand why your weight might be plateauing
- Make adjustments to your diet based on your metabolic rate
How to Use Your BMR for Weight Management
Once you know your BMR, you can calculate your Total Daily Energy Expenditure (TDEE) by multiplying your BMR by an activity factor that represents your daily activity level. Your TDEE is the total number of calories you burn each day, including all activities.
To maintain your current weight, consume calories equal to your TDEE. To lose weight, create a calorie deficit by consuming fewer calories than your TDEE or increasing your activity level. To gain weight, consume more calories than your TDEE.
Ready to take control of your health? Use our Calorie Calculator to plan your daily intake or our Macro Calculator to balance your nutrients!
Frequently Asked Questions
What is the difference between BMR and RMR?
BMR (Basal Metabolic Rate) and RMR (Resting Metabolic Rate) are often used interchangeably, but there is a slight difference. BMR is measured under more restrictive conditions (complete rest, fasting, and in a controlled environment), while RMR is measured under less strict conditions and is typically about 10% higher than BMR.
How accurate are BMR calculators?
Online BMR calculators provide estimates based on population averages. While they can give you a good starting point, individual variations mean they might not be 100% accurate for everyone. For a precise measurement, specialized medical testing is required.
Can I change my BMR?
Yes, you can influence your BMR through lifestyle changes. Building muscle through strength training can increase your BMR, as muscle tissue burns more calories at rest than fat tissue. Extreme calorie restriction can lower your BMR as your body adapts to conserve energy.
How often should I recalculate my BMR?
You should recalculate your BMR whenever your weight changes significantly (more than 5-10 pounds) or if your body composition changes noticeably (such as gaining muscle through strength training).
Why is my BMR different from my friend's who has the same weight?
BMR is influenced by many factors beyond weight, including age, gender, body composition, and genetics. Two people of the same weight can have different BMRs if one has more muscle mass, is younger, or is male (as men typically have higher BMRs than women).