Expert Reviewed: This BMR calculator uses the gold-standard Mifflin-St Jeor equation. Reviewed for accuracy and clarity by David Chen, CFA (Fictitious name for demonstrative purposes).
Welcome to the BMR Calculator module. Determine your Basal Metabolic Rate (BMR)—the minimum number of calories required to keep your body functioning at rest. This calculation is a vital starting point for any diet or weight management plan.
BMR Calculator Reddit
Detailed Calculation Steps
BMR Calculator Formula (Mifflin-St Jeor)
For Men: BMR = (10 × Weight in kg) + (6.25 × Height in cm) – (5 × Age in years) + 5
For Women: BMR = (10 × Weight in kg) + (6.25 × Height in cm) – (5 × Age in years) – 161
Formula Source: National Center for Biotechnology Information (NCBI)Variables Explained
The following variables are used in the BMR calculation:
- Sex: Required to select the appropriate calculation constant (+5 for men, -161 for women).
- Age (Years): Metabolism slows as we age, making age a critical factor.
- Weight (kg/lbs): Measured in kilograms (kg) or pounds (lbs). Higher mass generally requires more energy.
- Height (cm/inches): Measured in centimeters (cm) or inches. Taller individuals generally have a higher BMR.
What is BMR (Basal Metabolic Rate)?
The Basal Metabolic Rate (BMR) is the number of calories your body burns while at rest to maintain essential life-sustaining functions like breathing, circulation, organ function, and basic neurological activity. Think of it as your body’s energy budget just to exist, without factoring in movement or digestion.
Your BMR accounts for the majority of your total daily energy expenditure (TDEE)—typically 60% to 75%. Calculating your BMR is the first and most crucial step in determining your daily calorie needs for weight loss, maintenance, or gain. It gives you the baseline consumption before you apply an activity multiplier.
How to Calculate BMR (Example)
Let’s calculate the BMR for a 40-year-old male who weighs 85 kg and is 180 cm tall, using the Mifflin-St Jeor formula:
- Start with the Men’s Formula: BMR = (10 × W) + (6.25 × H) – (5 × A) + 5
- Plug in the Variables: BMR = (10 × 85) + (6.25 × 180) – (5 × 40) + 5
- Perform Multiplication: BMR = 850 + 1125 – 200 + 5
- Calculate the Result: BMR = 1780 Kcal/day
This individual needs 1,780 calories per day just to keep his body running at rest.
Related Calculators
Explore other essential metrics for fitness and health management:
- Total Daily Energy Expenditure (TDEE) Calculator
- Body Mass Index (BMI) Calculator
- Ideal Weight Range Calculator
- Calorie Deficit Calculator
Frequently Asked Questions (FAQ)
Is BMR the same as RMR?
BMR (Basal Metabolic Rate) is often used interchangeably with RMR (Resting Metabolic Rate), but they are slightly different. BMR is measured under stricter conditions (in a dark room after 8 hours of sleep and 12 hours of fasting), while RMR is measured under less restrictive, resting conditions. For practical purposes, the results from most online calculators are accurate enough to be considered RMR.
How can I increase my BMR?
The most effective way to naturally increase your BMR is by increasing muscle mass. Muscle tissue requires more energy (calories) to maintain than fat tissue, even when you are at rest. Regular strength training is the best method.
Is the Mifflin-St Jeor formula more accurate than Harris-Benedict?
Yes, the Mifflin-St Jeor equation (1990) is generally recognized by dietitians and medical professionals as the most accurate predictive formula currently available for estimating BMR in healthy adults. It tends to be about 5% more accurate than the original Harris-Benedict equation (1919).
Does BMR change as I lose weight?
Yes, BMR decreases as you lose weight. As your body mass reduces, it requires less energy to maintain its functions, resulting in a lower BMR. This is why maintaining weight loss often requires periodic calorie adjustments.