# BMI how to calculate

Body mass index (BMI) or Quetelet Index is a statistical measure to compare a person’s weight and height. In fact, BMI does not measure obesity, but it is a useful tool for estimating one’s weight according to height. Here are some tips on BMI and ideal weight calculation methods.

**What is Body Mass Index (BMI)?**

BMI is a measure of body fat and fitness based on a person’s weight-to-height ratio. This index is calculated by dividing the weight by the square of one’s height and it works well for people over 20 years old (male or female). The average figures for children over two years are different.

**BMI calculation formula**

Body mass index is obtained by dividing a person’s weight (in kilograms) by the height’s square (in meters).

The index was invented by Belgian scientist Adolphe Quetelet, which is why it is also called the Quetelet Index. It is very easy to calculate. Just put your height and weight in the formula above. You can also find your body mass index Here.

Suitable BMI for different age groups:

- 19-24 years = 22
- 25-34 years = 23
- 35- 44 years= 24
- 45-54 years = 25
- 55-64 years = 26
- 65 years and up = 27

These numbers indicate that you are underweight and have to gain weight or fit or overweight and have to lose weight.

**Adult BMI**

Since humans vary in height and body shape, BMI also shows normal weight relative to height. A higher BMI than normal indicates that you are heavier than your ideal weight. The area below the normal limit is counted for adults only.

BMI below 18.5:

- It means that a person is underweight.
- There can be many reasons for this result
- These people must seek to gain weight to gain health.

BMI between 18.5 and 24.9:

- This is a normal weight range
- If you are in this range, it means you are well-weighted
- However, these people should also follow a healthy diet with regular physical activity to maintain a healthy body and not go out of normal.

BMI between 25 and 29.9:

- This size is too ideal and you may be overweight, which means you are heavier than your height
- Overweight puts you at risk for heart disease, stroke and type 2 diabetes
- It’s time to react and start a diet and exercise program

BMI up 30:

- This size is the highest and is called obesity
- Obesity puts a person at risk for many diseases
- Losing weight very quickly has a positive effect on their health

**Children’s BMI**

As we said, BMI is calculated differently for children, although the procedure is similar to that for adults. But for children, it provides a percentage for comparing a child with children of his or her age and gender. To evaluate proper weight in children, specialists pay attention to the height, age, and gender of the child.

The result is called the BMI percentile. It is a good way to determine the proper weight of children and is done by specialists. The specialist using it can tell you whether the baby has grown as expected. When the BMI percentile is determined, the child falls into one of four groups:

- Underweight: Below the percentile 2
- Health weight: Between 2 and 90 percentiles.
- Overweight: Between 90 and 97 percentiles.
- Obese: 98 percentile or higher

If the child is above the normal range, it should be monitored to reach an ideal weight. Overweight causes problems for a child’s health. Studies show that overweight or obese children are at risk of obesity-related illnesses in childhood and later. So if you have a child with such a problem it is best to take action as soon as possible.

**How much is the ideal weight?**

Of course, sometimes you think about your weight and its number is important to you. The ideal weight depends on several factors, including:

- Height
- Gender
- The amount of fat and muscle
- Body frame size

**BMI is not always applicable!**

This index may be associated with an error coefficient for athletes and people with strong and dense muscle tissue and their BMI is higher than it is because it confuses the excess weight created by muscle tissue with excess body fat. There are also restrictions on the use of this index for the elderly because it may show these people’s overweight less than real. Also, calculating body mass index does not apply to pregnant women. In people between 18 and 20 years of age, the method of calculating body mass index for children should be used to obtain real numbers.