Medically reviewed by Suzanne Fisher, RD Key Takeaways Body mass index (BMI) is a calculation used to estimate your body fat.

Learn how to calculate Body Mass Index (BMI) using a free Windows app, online tool, or BMI Calculator software on Windows 11/10.

Muscle mass is a part of your lean body mass. It’s difficult to calculate lean body mass, let alone muscle mass, but there are some ways to get an idea of how much you have. Learn more.

Increasing the body's percentage of muscle mass can have various benefits. Here, learn to estimate this figure, as well as the percentage of fat.