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Trainers guide on calculating Body Mass Index (BMI)

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This blog post explains the concept of Body Mass Index (BMI), which is a formula used by personal trainers to determine an individual's body mass composition and set ideal weight goals for weight loss.

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Trainers guide on calculating Body Mass Index (BMI)

To chalk out a proper weight loss regimen, personal trainers first ascertain an individual's weight using the Body Mass Index (BMI). It's a formula that determines the body mass composition of the individual.

For personal trainers, BMI gives a quick measure to know whether a person is carrying excess body mass. Accordingly, the personal trainer sets the ideal weight goal and suggests the relevant weight loss exercises to achieve it.

What is BMI?

Body Mass Index (BMI) measures weight concerning one's height. It is the most frequently used index to determine one's body weight. The values in the index show whether a person is underweight, overweight, or obese.  

Thus far, BMI is an ideal weight body calculator. It is simple to use and is reproducible. But a drawback of BMI is it cannot determine body fat percentage. For instance, a person falling in the normal BMI range can have elevated body fat, which the BMI calculator cannot show.

Yet, BMI is the most preferred tool for determining healthy weight.

How to calculate BMI?

The formula for BMI calculation is

Formula: weight (kg) / [height (m)] ²

The formula is the same for both children and adults. A BMI reference chart with various BMI ranges and weight categories determines whether a person has a normal BMI.

For example, if a person weighs 75 kg and is 1.7m tall, the BMI would be as follows.

1.7 x 1.7 = 2.89

75kg ÷ 2.89 = 25.95

When you cross-reference with the BMI chart, you will know that the person is slightly short of a healthy BMI. The person falls under the overweight category.

Methods of calculating BMI

There are two methods of calculating BMI. But you need not worry about doing the calculations yourself. There are numerous BMI calculators available online that give values accurately.

  • Using Metric Measurements

The formula for BMI in a metric system is Weight in kilograms divided by height into meters or centimeters.

Weight (kg) / [height (m)] ²


[Weight (kg) / height (cm) / height (cm)] x 10,000

  • Using Imperial Measurements

In the imperial measurement system, the formula to calculate BMI is: Weight in pounds (lb.) divided by height in inches (in) squared and multiplied by a factor of 703.

Weight (lb.) / [height (in)] 2 x 703

BMI Chart for Men and Women

A BMI chart provides reference BMI values for a particular height. Though the formula for calculating BMI is the same for children and adults, the interpretation of the same is different.

The BMI value interpretation among children depends on gender and age. But for adults, there is no difference between genders. The BMI values for height and weight are the same for men and women.


Trainers prefer to calculate BMI for weight loss to determine one’s progress in their weight loss journey. It is not a complex measurement and does not require external interventions. Any BMI calculator will turn up accurate results. And personal trainers regularly use BMI for intervention and modify workouts or diet plans to achieve a healthy BMI.

What other methods do you prefer other than BMI for weight loss? Please share your knowledge with us.

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