BMI Calculator |Best Online Body Mass Calculator
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BMI calculator is an online tool to calculate bmi based on height, weight, age and gender. It estimates the fat content in the body in terms of body mass index ratio. This calculator is based on guidelines from Centers for Disease Control and Prevention (CDC), National Institude of Health (NIH) and World Health Organization (WHO) with added features and functionalities.
Guidelines for Using BMI Calculator
BMI calculator is an easy-to-use web-based app for accurate, reliable and body mass related results. Just access our website at bmicalcualtor.us and enjoy free calculations. The guidelines for using this tool includes following steps.
Step 1: First select the measurement units of your choice. You can either choose US based imperial (ft, in and pounds) system or international metric (cm, kg) system.
Step 2: Fill height and weight values based on your selected units.
Step 3: Also enter age and choose your gender for more accurate results.
Step 4: Click the “Calculate” button to output bmi value and its category.
Additionally, Body Fat Percentage, Basal Metabolic Rate (BMR), BMI Prime, Ponderal Index (PI), Weight to Lose or Gain to Maintain Healthy BMI are also calculated as results. These additional results are related to body mass and uses the same parameters for calculation as bmi does. It’ll save your time, calculating each value. Using this calculator will definitely help you in getting overall body mass related results just in single click. Hope you will enjoy it.
Definition of Body Mass Index (BMI)
Body Mass Index is defined as the ratio of person’s weight to height. According to WHO, it is a surrogate marker of fatness. This index is used to indicate whether a person is underweight, normal weight, overweight or in obese range. It is the primary and common method to estimate the fat content in the body.
The distribution of body fat and person's height greatly affect the bmi value. For example, tall people having weight of 90Kg may fall under Normal Weight category. But the same weight in case of short people may categorize them in Overweight. Thus, bmi is directly proportional to weight and is indirectly proportional to height’s square.
BMI Formula
The formula for bmi is weight divided by square of body’s height. While using different measurement system, the modified formula is as follow:
For Imperical/US system: BMI = Weight in Pounds / (Height in ft)2
For metrics system: BMI = Weight in Kg / (Height in cm)2
It’s unit is kg/cm2 (metric system) or lb/ft2 (imperical sytem). The other components such as age, gender, waist circumference are applied with special consideration.
BMI Categories for Adults
There are generally 4 categories in which bmi value is expressed namely, Under Weight, Normal Weight, Over Weight and Obese. The Under Weight is further classified as Severe, Moderate and Mild Thinness. Similarly, the Obese category is classified as Type I, II and III.
BMI Category Table
| BMI Range | Category |
|---|---|
| 0 - 17 | Moderate Thinness |
| 17 - 18.5 | Mild Thinness |
| 18.5 - 25 | Normal |
| 25 - 30 | Overweight |
| 30 – 35 | Obese Class I |
| 35 - 40 | Obese Class II |
| Above 40+ | Obese Class III |
BMI Chart
A visual representation of various categories of bmi (underweight, normal weight, overweight and obese) in the form of graphical representation is known as bmi chart. The chart is plotted against the height and weight where various different sections or color-coded areas are drawn to indicate specific category. It provides a quick access to determine the individual’s category based on theirs bmi value.
In order to use a chart, one need to locate their height and weight from the vertical and horizontal axis respectively. The point of intersection will give the bmi value and corresponding category in which they lie. Though it provides visual representation, the metrices like age, gender and other factors cannot be incorporated into the chart.
BMI Prime
BMI prime is defined as the ratio of calculated bmi of an individual divided by upper limit of normal bmi range. The upper limit for “Normal range” is generally considered as 24.9 or approx. 25. It provides comparative ratio between calculated and normal bmi value that helps to measure the deviation from a healthy range. The formula is given by:
BMI Prime = Calculated BMI/Normal upper limit
If the upper limit for Normal range is 25, then
BMI Prime = Calculated BMI/25
Since, bmi prime is the ratio between two same quantities, is unitless and dimensionless.
Division of Categories Based on BMI Prime
A BMI Prime of 1.0 indicates that a person is at the upper limit of a healthy weight, while values above 1.0 indicate overweight or obesity.
Interpretation of BMI Prime:
| BMI Prime | Category |
|---|---|
| Below 0.8 | Underweight |
| 0.8 to 1.0 | Normal weight |
| 1.0 to 1.2 | Mild Overweight |
| 1.2 to 1.5 | Moderate Overweight |
| Above 1.5 | Severe Obesity |
Ponderal Index (PI)
The Ponderal Index (PI) is an alternative measure of body composition that considers height and weight, similar to the Body Mass Index, but it uses a different formula. Though it is less common for expressing body mass, it is particularly more reliable method in short and tall persons. Some health experts uses PI value instead of bmi since it uses volume (cubic meter) to avoid overestimation of body fatness.
The Ponderal Index is calculated using the formula:
PI = Weight (Kg) /(Height in m)3
If calculated PI value is:
- 0-12: Underweight
- 12 to 22: Normal Weight
- Above 22: Overweight or obesity
Body Fat Percentage
It is the additional result that you can get by using this calculator. Body fat percentage is the measure of the proportion of fat to lean mass in the body. Theoretically, it is measured by using BMI method as follow.
- Body fat percentage for adult males = 1.20 × BMI + 0.23 × Age - 16.2
- Body fat percentage for adult females = 1.20 × BMI + 0.23 × Age - 5.4
- Body fat percentage for boys = 1.51 × BMI - 0.70 × Age - 2.2
- And for Girls, Body fat percentage = 1.51 × BMI - 0.70 × Age + 1.4
According to American Council on Exercise (ACE), the average accepted body fat percentage is about 39.9% for women and 28.1% for men. Below or above these range can lead to health risks. But these values may vary for athletes and film professionals.
Limitations of BMI
Body Mass Index is an anthropometry system to estimate the person’s fat content based on measurements of their weight and height. It is one of the primarily adapted methods for pre-clinical diagnosis and disorders related to obesity or leanness. Due to its non-invasive technique, the results may be circumscribed depending upon person’s age, sex and specific period such as diagnosis or pregnancy.
The bmi calculation is not applicable for pregnant women, growing children and seniors in some circumstances. Some additional terms and factors need to be considered to make the calculation reliable. Bmi does not distinguish between the fat and muscle. It includes both in the form of weight.
Thus, it is the main drawback because it categorizes the muscular person (e.g. body builders, athletes) into obese instead of normal category. The similar case is applied for older person who may contain visceral fat around the abdomen while the fat distribution on other body parts may be either reduced or normal. Thus, bmi can only be considered for preliminary treatment.