BMI Calculator For Runners

If you’re running to lose weight and tone up, knowing your BMI is a good first step. Here’s how to calculate it.


Photo: William Iven

One of the many benefits of running is that it burns calories faster than a lot of other types of exercise, so if you want to lose weight, running could be a big part of your program. Before you draft a weight loss and exercise plan, though, you’ll want to collect a little personal data, including your height, weight and BMI.

BMI Calculator

Related: See how many calories you burn running.

What exactly is BMI? Body mass index is a calculation of fat, in relation to a person’s height and weight. While the formula is not a precise measurement of the amount of fat in the body, estimating BMI is simpler and cheaper than other diagnostic assessments. Determining your BMI can provide a fairly accurate picture of whether you weigh too much or too little.

A high BMI may indicate a risk of certain medical conditions, such as heart disease, stroke, Type 2 diabetes and some cancers. A high BMI can also put stress on the heart, which may cause high blood pressure or gallstones. Other possible consequences of high BMI include back pain, osteoarthritis, excessive triglyceride and blood cholesterol levels, and low amounts of the healthy kind of cholesterol (HDL).

BMI Ranges

According to current criteria, these are the BMI ranges and their weight classifications:

  • A BMI below 18.5 is considered underweight.
  • A BMI between 18.5 and 24.9 is considered normal.
  • A BMI between 25 and 29.9 is considered overweight.
  • Those with a BMI over 30 are considered obese.

BMIs over 30 are divided into three grades: Grade 1, BMI is 30 to 34.9, Grade 2, 35 to 39.9 and Grade 3, 40 and higher.

What’s a healthy BMI? Generally speaking, the goal is to maintain a BMI of 18.5 to 24.9. A BMI index of 30 or more means a person is obese, but those who discover they meet this definition should not be too discouraged. Dropping just a few pounds, by altering diet and exercising more, can have a dramatic effect on BMI.

To estimate your BMI, use the following chart. Find your height in the left-hand column and your weight in the the top row. Then follow the two measurements to see where they intersect. This number is your BMI.  

The Limitations of BMI Measurements

BMI has its critics, partly because it usually doesn’t take into account different body types. For instance, runners and other athletes who maintain higher muscle mass might have a high BMI even though they are physically fit, and people whose muscles have weakened (such as the elderly) could have a low BMI despite being out of shape. However, if you’re looking for a baseline from which to start a weight loss program, estimating your BMI can be a good starting guideline for giving you a general sense of your ideal weight range.

The BMI measurement is by no means perfect. The basic calculation hasn’t changed since it was first developed in the 1800s. But it is a good starting point and should be used in conjunction with more accurate measures such as a body fat percentage test. The BMI calculation is unique in that it works for both men and women without having to change the calculation.

Some runners may have a BMI above the “normal” range of 18.5 to 24.9 but may have excellent cardiovascular health, low blood pressure and a slow, runners heart rate, while some within the normal range do not. This just underscores who BMI is just a starting point for determining a healthy weight range.