The body mass index (BMI) chart is an alternative way of finding out at a glance, what your BMI is. Using the BMI chart, you don't need to perform any calculations or enter any numbers into an on-line calculator. However, the BMI chart only gives you a BMI as a whole number, whereas calculating it will provide a slightly more accurate BMI score to decimal places, for example, 23.8 instead of 23 or 24 as found on a chart.


What is BMI and who can use the chart?

According to the CDC, the body mass index is an inexpensive and fairly reliable method of working out the amount of body fat someone has. It also provides a good indication of whether you are a healthy weight for your height. The body mass index chart is a standard reference guide of BMI figures for both men and women, but not children. Children are measured using different charts whereby they are compared against other boys or girls within their age groups as well as weight and height.

BMI chart limitations

While the body mass index chart is useful for most people, it does have limitations. For example, people with a lot of muscle mass tend to weigh more than the average person, simply because muscle is denser and weighs more than fat. Likewise, someone who is taller than average but has a small frame might still have excess fat around their middle but fit into the normal weight range. According to the Mayo Clinic, “People who gain belly fat are at greater risk of serious health problems, even death, than are people who accumulate fat in other areas”. Therefore, in some cases, doctors may want to use other devices for measuring body fat.

Understanding the BMI chart

Body mass index charts look like a large grid filled with rows of numbers. Along the top is a range of weights starting with the lowest on the left  through to the highest on the right. The left and sometimes the right side shows the heights with the shortest at the top and tallest at the bottom. Both weights and heights may be displayed in metric, imperial or both.

The numbers in the middle are the BMI figures and these are sometimes shaded according to category, for example red for obese and green for normal. Such charts will also feature a color-coded key. Those whose weight or height is outside the ranges shown on the chart may have to use a BMI calculator.

Using the BMI chart

Using the body mass index chart is easy and just involves cross referencing height with weight. For example, if you weigh 140lb and are 66 inches tall, look for your weight along the top, then move your finger down the chart until you arrive at the square which corresponds to your height on the left or right of the chart. The number you arrive at is your BMI. As stated earlier, it won't be exact, but it will provide you with a good indication of whether you should be concerned with your weight. The American Academy of Family Physicians Initiative (AIM), provides an excellent example of a body mass index chart for adults.

What the numbers mean

Your BMI number will fall into one of four or five ranges. The majority of BMI charts have four categories where a BMI of 18.5 or below is underweight, 19.0-24.9 is a healthy weight, 25-29.9 is overweight and above 30 is obese. Some charts also display a 'very obese' category. In the case above, the BMI is 23 and is therefore a healthy weight.

Understanding and using the body mass index chart is straightforward and simply involves cross referencing your height and weight to arrive at your personal BMI. You can then place your BMI into one of four categories ranging from underweight to obese. Remember, the BMI chart is only a guide and isn’t a definitive indicator to overall health. Always consult your doctor if you have any concerns over your BMI reading.