How to calculate your ideal weight!

Vonwarr

I've answered this question a few times, so I figured I would make a new post for more to see! Many on the forums know that BMI is a terrible tool to estimate your ideal weight... but for lack of a better way, many continue to use it, or just guess at what their ideal weight should be, or just try to reach a previous weight they happened to be previously.

There is a much better way to calculate your "ideal" weight than BMI! High lean body mass is good, we generally want to increase it as much as possible, it will increase our health and improve how we look. High fat mass is not so good, so we want to bring it down to a healthy level to look our best. BMI does not take this into consideration at all, it just blindly measures weight. Marc Perry from builtlean.com has a great article on this (linked below).

1. If you don't know it, calculate your LBM from your current BF %:

Lean Body Mass (LBM) = Your Body Weight – (Your Body Weight x Your Current Body Fat Percentage)

2. To find your ideal weight, start with your LBM... then add a healthy percentage of fat:

Lean Body Mass/(1- Desired Body Fat Percentage)

For example, I have 150 lbs of LBM. According to the charts (linked below), as a male at my age (26), the middle of the "ideal" range is... around 13%. So... 150/(1-0.13) = 172.5. My ideal weight would be basically between 170-175.

That would put me into the "overweight" BMI category at 26.1... however, I have a high amount of lean mass for someone my height (5'8"). To reduce my weight into the "healthy" range according to BMI would mean going down to 164 to reach a BMI of 24.9. That would put me at 8.5% body fat and I would look pretty ripped just from the lack of BF.... but most often unless someone is working REALLY hard to maintain their muscle, they can drop muscle instead of (or as well as) fat. That's when you get a "sickly" look - even though BMI is telling you that you're in your "ideal" range.

tl;dr - BMI is stupid, calculate your ideal weight


References:
http://www.builtlean.com/2010/05/04/ideal-body-weight-formula-how-to-calculate-your-ideal-weight/

How to find your desired fat percentage... scroll down to the rainbow charts:
http://www.builtlean.com/2010/08/03/ideal-body-fat-percentage-chart/

SouthernSweetie74

Thanks for posting! I've used this calculator before, but I have a question.

I go to a weight loss clinic where they measure body fat %, fat free mass, etc.

My fat free mass (is that same as lean body mass? I'm guessing it is) is 138. And I'm one of these females that still wants to keep my curves and a little bit of squishiness in all the right places, so I'm thinking body fat % should be around 22%. I think that's within the range my doc told me to shoot for as well. So when I calculate that out, that puts me at an ideal weight of 176. But, in order for that to be correct, I would have to maintain my lean body mass and not lose muscle, right? But don't you normally lose some muscle when you lose weight? I already have. I started with 150 pounds of fat free mass. So, of the weight I've lost, 12 pounds of it was the wrong stuff.

Do I need to start lifting heavy? HELP.

High protein, low carbs? Would that help?

Vonwarr

Fat free mass is the same as lean body mass. 22% BF is a great target to shoot for. For that weight to be right you would have to maintain your lean mass. You can re-adjust the calculation if you lose a bit of lean mass as well. There's nothing wrong, just that your target weight will be a little lower according to this calculation.

Losing LBM isn't the end of the world! It's ideal to maintain or more practically, minimize your loss of LBM. Lifting heavy and high protein helps you maintain lean mass... but it's not absolutely necessary.

SouthernSweetie74

Thank you!