What is BMR Calculator?
Basal Metabolic Rate, also known as BMR, describes the amount of energy that the human body burns daily to maintain its vital functions just to survive.
In other words it gives you an approximate number of calories you would burn if you spent an entire day doing nothing, the minimum amount of energy needed to keep the body alive, which includes vital functions such as breathing, digestion and heartbeat.
BMR calculator does not account for the energy you expended in your daily activities or exercise.
Imagine spending a whole day without any physical effort, on an empty stomach, at an ambient temperature of 20 °- 25° Celsius, in complete peace. Surprisingly, during that time your body needs energy and burns calories anyway.
It does sound like a paradox, that the body needs the most calories and energy while relaxed, because every organ in our body is considered “a muscle”. The muscles that need a lot of energy for their proper functioning.
You might find it surprising that about 70% of our calories are burned to maintain those daily physiological, vital functions of the organs, like: breathing for lungs, pumping for heart , digesting for intestines, filtering blood for kidneys and so on.
So if you don’t eat enough, you risk leaving your organs without energy to work.
The energy that the body burns during the day is called total daily energy expenditure (TDEE). This concept is divided into 3 groups: basal metabolism, thermic effect of food, and level of physical activity.
From which most of the energy goes to basal metabolism
When you know your BMR, you know exactly how many calories you burn during the day while at rest. Thus, you can evaluate how many calories you need to take in order to increase muscle mass, lose weight, or maintain it. Simply put, if you know how many calories you are taking in and burning, the path to a perfect body will be easier.
To find out the number of calories your body needs, you can use the BMR calculator or do the calculation yourself using formulas.
Remember that you can not know exactly what the BMR value is by using a BMR calculator. The only way you can figure out 100% BMR results is through laboratory testing with help of a specialist using – indirect calorimetry which measures the rate of oxygen consumption, for this test person needs to fast for 12 hours and be at neutral temperature, to prevent sweating or chills.
You can visit a nutritionist for exact BMI, BMR, Fat %, lean muscle records, etc to plan a diet accordingly and accurately.
There are 3 main types of BMR calculator formulas:
- The Mifflin-St Jeor formula
For men: BMR = 10 x Weight + 6.25 x Height – 5 x Age + 5
For women: BMR = 10 x Weight + 6.25 x Height – 5 x Age – 161
For this BMR calculator we use the Mifflin-St Jeor formula, which is considered to be the most accurate and most commonly used BMR equation nowadays.
- Revised Harris-Benedict Formula:
BMR = 13.397 x W + 4.799 x H – 5.667 x A + 88.362
BMR = 9.247 x W + 3.098 x H – 4.330 x A + 447.593
The older Revised Harris-Benedict Formula was introduced in 1984, although its popularity waned in the 1990s , when newer more accurate formulas were presented. This formula is likely to over and under-estimate results for very muscular or very obese people, thus it’s less commonly used nowadays.
- Katch-McArdle formula
BMR = 370 +(21,6 x Lean Body Mass(kg))
In case you know your body fat %, formula looks like this
BMR = 370 + 21.6(1 – Body fat %) x Weight
Recently, a newer Katch-Mcardle formula was developed, which differs from other formulas only in that it calculates energy expenditure during rest (RDEE), also taking into account muscle mass and body fat percentage. This formula is more suitable for the slimmer people who are looking to increase muscle mass, when used properly this formula is considered to be very accurate.
BMR Calculator – Factors that Affect BMR
BMR is influenced by several factors:
- Weight – people with higher weight will get a higher BMR count
- Body type – it is known that adipose tissue has a lower metabolic activity than muscle tissue. As muscle mass and body surface area increases, so does the metabolic rate.
- Age – metabolic rate decreases with age, the reason for this is the loss of muscle tissue, the growth of adipose tissue, as well as hormonal and neurological changes.
- Gender – basal metabolism in males is about 5-10% higher than in females. This is because women have more body fat than men of the same weight and height.
- Genetics – you’re are more likely to have similar BMR as your parents or other first-degree relatives, genetics play a huge role in determining your metabolic rate.
- Body temperature – for every 0.5 ° C increase in body temperature, BMR increases by 7%.
The first step in calculating the number of calories is to calculate BMR using any of the three methods mentioned.
The second step is to find out your total daily energy expenditure (TDEE) , for that we need to multiply the final BMR number by the factor of level of your physical activity, which has 5 types:
- Passive type – if you have minimal or no physical activity, multiply BMR by a factor of 1.2.
- Minimally active type – if you train 1-3 times a week, multiply BMR by a factor of 1.375.
- Moderately active type – if you train 3-5 times a week, multiply your BMR by a factor of 1.55.
- Active type – if you train 5-6 times a week, multiply your BMR by a factor of 1.725.
- Overly active type – if you are a professional athlete or train 6-7 times a week or have a physically demanding job, multiply BMR by a factor of 1.9.
The final number represents the energy requirement and the calories you need every day to maintain your weight. If you want to lose weight, you need to take in fewer calories and vice versa.