• Home
  • /
  • Blog
  • /
  • How Do BMI Scales Work? A Definitive Guide
July 25, 2022

With the current obesity epidemic, more and more people are interested in their Body Mass Index (BMI). BMI scales are a quick and easy way to get an idea of whether someone is a healthy weight, overweight, or obese. But how do these scales work?

This guide will explain everything you need to know about BMI scales, including how they are calculated and what they can tell you about your health.

What is BMI?

Body Mass Index (BMI) measures body fat based on height and weight. It is used to calculate whether someone is a healthy weight, overweight, or obese.

BMI is calculated by dividing a person’s weight in kilograms by their height in meters squared.

BMI= Weight in kg / (Height in meters x Height in meters)

For example, a person who weighs 70 kg and is 1.7 m tall would have a BMI of 24.2.

The BMI scale ranges from underweight (a BMI of less than 18.5) to obese (a BMI of 30 or above). A BMI of 25-29.9 is considered overweight, while a BMI of 18.5-24.9 is considered healthy.

  • Below 18.5 – Underweight
  • 18.5 – 24.9 – Normal or healthy weight
  • 25.0 – 29.9 – Overweight
  • 30.0 and Above – Obese

How Do BMI Scales Work?

BMI scales use height and weight to calculate BMI. The scale then uses BMI to determine whether someone is underweight, a healthy weight, overweight, or obese.

There are two types of BMI scales: analog and digital. Analog scales are the older scale and use a needle to show BMI. Digital scales are newer and use a display to show BMI.

  • To use an analog BMI scale, you must first input your height into the scale. Then, you stand on the scale, and the needle will move to show your BMI.
  • To use a digital BMI scale, you first need to input your height and weight into the scale. Then, the scale will calculate your BMI and show it on display.

What Do BMI Scales Tell You?

BMI scales can tell you whether you are a healthy weight, overweight, or obese. They can also tell you if you are at risk for health problems such as heart disease, stroke, and diabetes.

  • If you are overweight or obese, your doctor may recommend making lifestyle changes to lose weight. These changes may include eating a healthy diet and getting more exercise.
  • If you are underweight, your doctor may recommend gaining weight. This can be done by eating more calories or taking supplements.

Overall, they are important for several reasons. They help healthcare professionals assess whether a person is at a healthy weight. Also, BMI scales can be used to track changes in weight over time. Furthermore, can help identify individuals who may be at risk for obesity-related health problems.

BMI Scales Work

What Are The Limitations of BMI Scales?

BMI scales are not perfect. They may not be accurate for people who are very muscular or have a lot of body fat. BMI scales also do not consider age, sex, or race. Also, they do not measure body composition and a person’s body fat percentage. Despite these limitations, BMI scales are a quick and easy way to get an idea of whether someone is a healthy weight, overweight, or obese.

BMI Vs. Body Fat Scales

Body mass index (BMI) and body fat percentage are the two most common ways to measure weight. But which is a better indicator of health?

  • Body mass index (BMI) is a measure of body fat based on height and weight that applies to both adult men and women.
  • On the other hand, body fat percentage is the fat tissue proportion of total body weight. The most accurate way to measure body fat percentage is with a scale that measures the amount of body fat resistance.

So, Which Is A Better Measure Of Health?

There are pros and cons to both BMI and body fat percentage.

  • Body mass index is a good indicator of overall health for most people. It is easy to calculate and is widely used by healthcare professionals. However, BMI does have some limitations. For example, it does not consider fat-free mass, age, body composition, or bone density. This means that athletes and people with high muscle mass may have a higher BMI but be at a healthy weight.
  • Body fat percentage is a more accurate measure of health for people with more muscle mass or who are athletes. It is also better for people over 65, who generally have lower muscle mass.

You can use a body fat scale or caliper to calculate your body fat percentage. Body fat scales use bioelectrical impedance analysis (BIA) to estimate your excess body fat percentage. BIA works by sending a small electrical current through your body. The current travels more quickly through water and muscle than through fat. The scale can estimate your body fat percentage by measuring how long the current travels through your body.

A body fat caliper is a device that measures the thickness of a fold of skin and fat. The caliper is placed on the skin, and the skin and fat are pinched into the caliper’s jaws. The caliper measures the thickness of the skinfold, which is then used to estimate body fat percentage. Also, dual-energy X-ray is one of the body composition scales.

Both BMI and body fat percentage have their advantages and disadvantages. However, both are good indicators of overall health. If you are concerned about your weight, talk to your healthcare provider about which measure is right for you.


BMI scales are a quick and easy way to assess whether someone is at a healthy weight. While they are not perfect and should not be used as the sole measure of someone’s health, they can indicate whether someone is at a healthy weight. If you are concerned about your weight or are trying to lose weight, talking to a doctor or dietitian can be a good way to get more information and support.

BMI Calculator