Calculating your fat and lean weight is a straight forward task and should be done regularly to track progress. To measure this you’ll need two things up front, your weight in lbs and your current body fat %. Read about calculating body fat here.

Once you have those, use this method to calculate your fat weight.

Calculating fat weight

Body weight (lbs) x body fat % (in decimal form) = Fat weight

In example:

A person weighing 180 lbs, with a body fat of 15%…

180 x .15 = 27 lbs of fat

Calculating lean weight

To calculate you lean weight (or Lean Body Mass/LBM), simply take your weight, minus fat weight. Following the example above:

180 lbs – 27 lbs = 153 lbs of lean weight

Why take these measurements?

Regularly measuring your lean weight and fat weight (every week or so) can indicate if your program is on track and you aren’t losing too much in the way of muscle, or indeed losing too much fat, too quickly.