What’s My BMR And How Do I Calculate It?
You’ve probably heard of ‘BMR’ being tossed around when talking about calories and what your body needs to lose, gain, or maintain weight. However, you probably don’t know much about it, and chances are if you’re here reading this, you’ve wondered to yourself ‘what’s my BMR’ and maybe even how you calculate it. Believe it or not, our bodies need calories at complete rest to perform basic functions, even when sedentary, and this is where the importance of knowing your BMR comes into play.
Ready to figure out what’s BMR once and for all? Let’s dig in! BMR stands for basal metabolic rate and is a common equation that nutrition coaches, nutritionists, dietitians and personal trainers use to calculate the amount of calories an individual’s body needs on a daily basis for essential functioning. Essential functions that BMR accounts for are mostly the involuntary things that our bodies do to support us staying on this side of the pavement, so to speak.
These involuntary things are:
- Circulating Blood
- Body Temperature Regulation
- Nervous System Operation
- Eyes Blinking
- Lungs Breathing
- Heart Beating/Heart Rate
- Brain Function
- … and more!
What's BMR Good For
As you can tell from the list above, the basal metabolic rate (BMR) that our body has is essential to staying alive. Keep in mind that BMR does not account for calories/energy needed by the body to perform other non-essential functions or activity throughout the day. It’s also important to note that BMR is an estimate, and an estimate that accounts for the minimum amount of calories an individual should consume on a daily basis to maintain positive, healthy functioning, while in a resting state.
What’s My BMR
BMR is the amount of energy from food that we need to live. The formula is called the ‘Harris-Benedict equation’ and it is different for men and women. Everyones BMR is different. Age, gender, size, height, weight, mass, sleep, internal organ size, and even genetics influence body composition.
BMR vs RMR
While some people use BMR and RMR (resting metabolic rate) interchangeably, it’s important to note that while the two are similar, they are not the exact same.
Basal Metabolic Rate (BMR)
The number of calories your body needs to perform the most basal (basic) functions. The most accurate way to calculate BMR is in a lab setting, but it can be estimated outside of a lab environment. The testing requirements for BMR in the lab have requirements such as fasting for 12 hours before the test, sleeping for 8 hours prior to the test, being monitored in a darkened, temperature-controlled room, and remaining in a reclined position.
Resting Metabolic Rate (RMR)
The number of calories your body burns at rest. RMR is typically measured before eating or exercising in the morning after someone wakes up or during a period of inactivity. This is a less stringent test and calculation because the testing conditions are less specific. This is often the most accurate way of estimating caloric demands from the body at rest as compared to BMR.
How To Calculate The Basal Metabolic Rate
If you came to this article wondering ‘how to calculate my BMR’ then you’ve definitely come to the right spot. The first way we’ll talk about calculating BMR is by using a pretty simple equation, called the Harris-Benedict Equation. For this hand calculation you will need to know your weight in kilograms, your height in centimeters, and your age in years. It’s important to note that this is a very big estimate and it is difficult to accurately test this with the basic equation.
- Men: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) - (5.677 x age in years)
- Women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) - (4.330 x age in years)
Once BMR is determined with the above formula, then you can begin to factor in exercise considerations.
- Little to no exercise: BMR x 1.2
- Light exercise (1-3 days per week): BMR x 1.375
- Moderate exercise (3-5 days per week): BMR x 1.55
- Heavy Exercise (6-7 days per week): BMR x 1.725
- Very heavy exercise (2x per day, performance/athletic training): BMR x 2
Free BMR Calculator - Online BMR Calculator
If you’re not real ready to calculate out your BMR by hand, you can input your height, weight, and age into our online BMR calculator to determine your BMR. You’ll also be able to calculate in your daily activity to give you a more accurate look at the total number of calories you burn each day.
How To Calculate RMR
As stated previously, calculating RMR is a more accurate way of estimating caloric demand. To calculate RMR, there are two different equations. The first is the Revised Harris-Benedict BMR equation and the second is the Mifflin-St Jeor Equation. Both provide different equations for men and women, yet both are still just an estimate. To calculate your RMR, you will need your weight in kilograms, height in centimeters, and age in years. Lastly, we’ll also note that the Mifflin-St Jeor Equation is often more favored than the Revised Harris-Benedict BMR equation.
Revised Harris-Benedict BMR equation
- Men: (88.4 + 13.4 x weight) + (4.8 x height) – (5.68 x age)
- Women: (447.6 + 9.25 x weight) + (3.10 x height) – (4.33 x age)
Mifflin-St Jeor equation
- Male: 9.99 x weight + 6.25 x height – 4.92 x age + 5
- Female: 9.99 x weight + 6.25 x height – 4.92 x age – 161
Free Online RMR Calculator
Similar to the free BMR calculator above, you can use this handy, free online RMR calculator to figure out your caloric estimate for what your body burns at rest.
How To Use BMR To Lose Weight
Depending on the above BMR calculation, you adjust to eat less, eat, or eat more as the amount of energy presented. This is where the concept ‘calories in vs calories out’ comes into play. If you want to lose weight, you eat less than you use on a daily basis. If you want to maintain, you eat the same. If you want to gain, you eat more.
Now if you’re looking to optimize your body composition and do a little more than just lose, maintain, or gain, this is where macro tracking and macro counting can come into play. This method of tracking the calories you eat breaks down the calories into three different categories - protein, carbohydrate, and fat. When you begin to manipulate these calorie contributors, you can increase/decrease lean muscle mass, change body fat composition, or adjust other things like performance indicators and glycogen stores. Macros are a different set of calculations, but they do consider both BMR and activity respectively.
RELATED: 1:1 Customized Macro Coaching
What’s My BMR: Takeaway
While calculating BMR is a big estimate and RMR is a more accurate way to estimate our bodies needs, it is definitely a good question to ask - what’s my BMR. With online calculators, formulas, and revised formulas, the information provided above should sufficiently provide you with a general estimate on what to shoot for calorie wise on a daily basis to start working towards your goals. After you begin to understand the concept behind ‘calories in vs calories out’ you can then begin to breakdown calories into macronutrient groups, like protein, carbs, and fat, to begin to optimize your body composition even further.
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