The formula for calculating lean muscle mass is as follows:
Lean Body Mass = Total Weight * (1-(bodyfat % *100)
How to measure body fat percentage
The most accurate way to perform this calculation is to use body calipers and take measurements from each of the different areas of the body. The typical no. of measurements if taken from 3 different places, but also up to 7. The specific sites used vary in men and women.
For women, the triceps, area above the hip bone and either the thigh or abdomen are used for the 3-site measurement (2). For a 7-site measurement in women, the chest, area near the armpit and area beneath the shoulder blade are also measured.
For men, the 3 sites are the chest, abdomen and thigh, or the chest, triceps and area beneath the scapula (2). For a 7-site measurement in men, the areas near the armpit and beneath the shoulder blade are also measured.
However when using this method it is best to make sure you use a professional who is skilled at using calipers in order to ensure an accurate reading.
Bioelectrical impedance analysis (BIA)
BIA devices detect how your body responds to small electrical currents. This is done by placing electrodes on your skin. Some electrodes send currents into your body, while others receive the signal after it has passed through your body tissues.Electrical currents move through muscle easier than fat due to the higher water content of muscle.
The BIA device automatically enters your body’s response to the electrical currents into an equation that predicts your body composition.
The accuracy of these devices largely depends on the quality of them. There are top of the range devices available to use in many gyms these days. Alternatively you can purchase BIA home scales for between £20 to £100 for use at home. I personally recommend you do this so that you can conduct regular progress checks.