To calculate lean body mass (LBM), you need to subtract your body fat from your total body weight- Lean body mass represents the weight of everything in your body besides fat- including muscle- bones- organs- and fluids.

Here's how you can calculate it.

Measure your Body Fat Percentage: You can do this using various methods such as skinfold calipers, bioelectrical impedance analysis (BIA), DEXA scans, or body fat scales. Let's denote this as BF%.

Calculate Lean Body Mass (LBM):

LBM = Total Body Weight - (Total Body Weight * (BF% / 100))

Here's a simple example:

Let's say your total body weight is 70 kilograms (kg), and your body fat percentage is 20%.

LBM = 70 kg - (70 kg * (20 / 100))

= 70 kg - (70 kg * 0.20)

= 70 kg - 14 kg

= 56 kg

So, in this example, your lean body mass would be 56 kilograms.

Remember, this is just an estimation, and actual LBM can vary based on factors like hydration levels, muscle mass distribution-etc- For a more accurate measurement- you may want to use more precise methods like DEXA scans.