By Nancy Szokan

The Washington Post

Most people know that BMI, or body mass index, is a fitness indicator calculated using your height and weight. Most people also know (don’t you?) that where you carry your weight makes a difference: It’s less healthy to have a disproportionate amount of weight around your midsection.

The April issue of O (the Oprah magazine) features a calculator aimed at factoring that belly fat, as well as your age, into the equation and assessing your relative risk of premature death. Called A Body Shape Index, or ABSI, the formula involves such complicated steps as calculating BMI, then raising it to the two-thirds power. The developers explain in the July 2012 issue of the journal PLOS One why they think it is a useful estimate of mortality risk.

If you’d rather skip the science-speak, go to the Web address above to plug in your age, height, weight and waist measurement. If the “Relative risk, BMI+ABSI” comes out as 1, that puts you at average risk of premature death for someone your age; less than 1 indicates less risk; and greater than 1 means … well, you might want to start doing some crunches.