# How to Calculate Body Mass Index

Body mass index, also known as BMI, is a calculation to help determine whether or not you are overweight. The calculation takes into consideration your weight in relation to your height, and comes up with a number that is an accurate barometer as to whether or not you need to lose weight.

Many health websites are equipped with a BMI calculator that does the work for you. With a BMI calculator, all you have to do is enter your height and weight, and the tool pops out your final BMI reading. A body mass index of 18.5 or less means you are underweight. A healthy weight falls between 18.5 and 24.9, with the overweight category between 25 and 29.9. If you have a body mass index over 30, it means you are technically obese. Some people with BMI readings into the 30’s and 40’s may be eligible for weight loss surgery to help correct the problem before they suffer serious health consequences.

If you are unable to get to a website that has a BMI calculator, you can figure out your reading manually. All you need is a piece of paper, a pencil and a regular calculator. Using your imperial measurements, the calculation is as follows: Weight in lbs / (height in inches x height in inches) x 703. The metric calculation is as follows: Weight in kg / (height in meters x height in meters). As an example, for a 180 lb person who is 5’6, or 66 inches tall, the calculation would be 180 / (66 x 66) x 703, which equals a BMI of 29. For a metric reading, a person who is 65 kg and 1.7 meters tall would read 65 / (1.7 x 1.7) which equals a BMI of 22.5. Figuring out your BMI manually is accurate and will give you a true reading, but a BMI calculator is much more convenient if you’re able to find one.

In some cases, a BMI reading will suggest weight loss is necessary when it really is not. For people who train regularly with weights, their muscularity will add weight that the BMI calculator can’t differentiate from fat. If a weight lifter or bodybuilder is of average height, the BMI reading may suggest he is obese, when that definitely is not the case. On the other side, some older people who have lost quite a bit of muscle may get a BMI reading that is lower than their overall fat content would indicate. Weight loss may be a wise choice, but the BMI numbers won’t agree.

However, in the majority of cases, your BMI number is a true reflection of the state of your body composition. It is important for people with a high BMI to lose weight, as carrying added pounds is associated with health risks such as arthritis, heart disease, stroke and type 2 diabetes. Punch your height and weight into a BMI calculator online, or figure out your BMI manually to help gauge whether it is time to lose weight or if everything is just fine.