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If your goal is to lose, maintain, or gain weight, calculating your Basal Metabolic Rate (BMR) is an essential first step. BMR represents the energy your body burns while at complete rest, essentially supporting vital functions such as organ operation and keeping you alive, without factoring in physical activity. Your BMR is influenced by many factors, including gender, age, height, and weight, but your body fat percentage, diet, and exercise routine also play key roles. Keep reading for a simple process that both men and women can follow to calculate their BMRs.
Steps to Follow
BMR Calculators
Male BMR Calculator
Female Basal Metabolic Rate (BMR) CalculatorHow to Calculate BMR in Men
Measure your height in centimeters. Your BMR is generally higher the larger your body frame. For example, a taller man has more body mass, which results in higher daily energy expenditure. If you're unsure of your exact height, get an accurate measurement. Always use centimeters for BMR calculations as they are based on metric units.
- Stand against a wall with your back straight and heels touching the surface. Have someone mark the top of your head. Then, measure the distance from the floor to the mark using a tape measure to get your height.
- If you're used to measuring height in inches, multiply your inches by 2.54 to convert them to centimeters.
Weigh yourself in kilograms. If it's been a while since your last check, step on the scale. Heavier individuals tend to burn more calories daily due to increased body mass. Weighing yourself is also crucial when tracking weight loss or gain goals, as it gives you a baseline to judge your progress.
- If you have your weight in pounds, you can multiply it by 0.454 to convert to kilograms.
- Remember, your weight fluctuates throughout the day—due to meals, drinks, or bathroom use—so if you’re monitoring your weight, weigh yourself weekly at the same time of day with similar clothing.
Apply the BMR formula for men. Men’s BMR is calculated using the following equation: BMR = 66 + (13.8 x weight in kg) + (5 x height in cm) - (6.8 x age in years). This formula takes into account key factors like height, weight, age, and gender. Generally, BMR increases with height and weight but decreases with age.
- The BMR value is expressed in kilocalories per day, or simply "calories" in everyday terms. These calories are familiar to you from nutritional labels on food packaging.
Consider other factors that can influence your BMR. While the BMR equation provides a convenient estimate, it's not a flawless tool. Several factors, beyond just height and weight, can alter your personal BMR, including:
- Muscle mass: Individuals with more muscle tend to have higher BMRs. For instance, a 200-pound Olympic swimmer with minimal body fat will burn more energy at rest than a 200-pound man with moderate fat levels.
- Growth: People undergoing rapid growth, like adolescents or those recovering from injury, may experience a higher BMR.
- Body temperature: A rise in body temperature, such as during a fever, can accelerate BMR.
- Diet: Drastic dieting or fasting can reduce BMR as the body adapts to function with less fuel.
- Heredity: Some people inherit a faster metabolism from their parents. If you know someone who can eat without gaining weight, they've likely inherited a high BMR.
How to Calculate BMR in Women
Measure your height and weight. Just like in men, BMR varies significantly among women based on these factors. For accurate BMR results, measure your height and weight precisely, and use metric units—centimeters for height and kilograms for weight—as the BMR formula assumes metric measurements.
- To convert inches to centimeters, multiply by 2.54. To convert pounds to kilograms, multiply by 0.454.
- If you're working on losing or gaining weight, weigh yourself at the same time each week. Weight can fluctuate by up to 5 pounds due to normal daily activities.
Apply the BMR equation for females. Women typically have lower BMRs than men due to lower amounts of lean body mass, which is the total body mass minus fat. The female BMR equation adjusts for this by using smaller multipliers for height and weight. Interestingly, women's metabolisms slow less drastically with age compared to men's, so the factor applied to age is also smaller. The formula for women is: BMR = 655 + (9.6 x weight in kg) + (1.8 x height in cm) - (4.7 x age in years).
- The result is in kcals (calories) per day.
Understand how pregnancy affects BMR. Just as factors like diet, growth, body temperature, and muscle mass influence BMR in men, pregnancy can notably impact a woman's BMR. Pregnant (or breastfeeding) women experience higher BMRs due to the extra energy required to nurture an infant and produce breast milk. If you've observed an increase in appetite during pregnancy, this is a clear example of BMR elevation in action.
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Once you've determined your BMR, you can apply an activity multiplier to estimate your Total Daily Energy Expenditure (TDEE), which gives you a better idea of how many calories you burn in a day. The activity multipliers are as follows: 1.2 for sedentary individuals, 1.375 for lightly active individuals (light exercise 1 to 3 days per week), 1.55 for moderately active individuals (moderate exercise 3 to 5 days per week), 1.725 for very active individuals (intense exercise 6 to 7 days per week), and 1.9 for extremely active individuals (high-intensity daily training or more than one session per day).
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If you’ve assessed your body composition, you can use your lean body mass to more accurately calculate your BMR. Lean body mass represents the weight of your body minus the fat. The formula to calculate BMR based on lean body mass is: BMR = 370 + (21.6 x lean body mass in kg)
Important Warnings
- The standard BMR formula works well for most individuals. However, it doesn’t account for the muscle-to-fat ratio, which means it may underestimate the caloric needs of a highly muscular person and overestimate those of someone with a high body fat percentage. If you're very lean or obese, consider using the formula based on body composition for more accurate results.
