Lean Body Mass Calculation Error

edited April 2018 in Bug Reports

Here's the calculation for lean body mass that every other calculator uses:

I'm going to use the example of a 240 pound person with BMI of 43.

Step 1
Weigh yourself with a body fat scale. The scale will automatically calculate your percentage of body fat. (Body fat % = 43)

Step 2
Subtract your body fat percentage from 100 to get your lean mass percentage. (Lean mass PERCENTAGE = 100-43 = 57)

Step 3
Divide your lean mass percent by 100 to calculate the decimal for your lean mass percent.
(This just gets you to 0.57.)

Step 4
Multiply your lean mass decimal by your total body weight to calculate your lean mass weight. (240 lbs x 0.57 = 136.8 lbs. of lean mass)

Step 5
Multiply the LEAN MASS, NOT THE LEAN MASS PERCENTAGE by 0.8. (136.8 lbs * 0.8 = 110 g/lb)

Your calculator is stopping at Step 2. You're multiplying the lean mass PERCENTAGE, not the actual LEAN MASS VALUE.

Also, in many of the responses on this discussion board, I have seen your experts say we need between 0.8 g - 1 g per Kg. That is not right. It's 2.2g/Kg of lean BW. 0.8 - 1g PER lb.

1 gram of protein per pound of body weight (2.2 g/kg of BW) per day has been a bodybuilding rule of thumb for decades. Higher levels of protein intake, usually in the range of 1.2 – 1.5 grams per pound of body weight (2.6 – 3.3 g/kg BW) per day, are commonly recommended when “cutting” to lose fat.

This really needs to be addressed. There's a HUGE difference between what your calculation would show for that person and what they really need to be shooting for - 45.6 g vs 110 g. You've more than halved the protein they need. I'm sure it's more extreme, the larger a person is...


  • I've checked the math and we're doing everything correctly (steps 1 — 5).

    I believe you're taking issue purely with our default presets (ie. the 'moderate' preset has 1g per kg of LBM). You can choose 'Custom' from the list there and change that 1 to 2.2 or any other value you see fit.

    We'll look at updating the presets available in the future, but the current presets were designed with medical ketogenic therapies in mind (i.e. not for general weight loss / fitness), where protein does need to be more tightly controlled.

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