How Do I Calculate How Much Weight To Lose Based On Goal BF%?

[Roofus]

I've tried the numbers but math is simply not my strong suit. What I'd like to figure out is my goal weight loss based on the BF% I would like to achieve. Now I realize it won't be dead on because it's possible I gain a couple pounds of mass during the process. But I'm sitting at 178lbs at 12%BF. My goal is 7%BF. So I'd like to figure out how much additional weight I need to drop to decrease my BF by 5%.

If I'm 178lbs at 12%BF then that means I'm carrying 21lbs of fat. So 178 - 21 = 157lbs which would be my weight with 0BF%. But this is where I get stuck. Because obviously if I figure 7% of 157lbs then that's not right. Do I take roughly 65% of the 21lbs and add it to the 157? I'm confused. Science... Help!

I realize in the end the figure won't be perfect because of other factors. But to know I need to lose roughly 8lbs for example would just be a nice motivational tool for me.

 

[chaos13]

178lbs * 12% bodyfat = lean body weight (156.6lbs)

(156.6lbs * 7% bodyfat) + lean body weight = with 7% body fat, assuming level of lean muscle mass is retained, total weight would be 167.6


So you would want to lose 178-167.6 = 10.4lbs of weight

 

[Roofus]

I think what you're doing there is fairly close to accurate, but I'm not sure that's totally correct. Because if you work it backwards it doesn't compute. When you multiply 156 by 7% you're calculating 7% of 156. Whereas BF would be 7% of a higher value...roughly 167.

If you work your numbers backwards you'll get something different. For instance if we used that calculations on some easier figures:

(200lbs (0%BF) x 10%BF) + lean body weight = 220lbs

What you're saying is that 220lbs should now be an individuals total weight at 10%BF. But now if we take 10% of 220, you arrive at 22lbs BF, and the individuals lean body mass would be 198lbs.

So our calculation is still a little off. Nontheless, I think at those percentages it's so close that for me personally it is a moot point. It's roughly 10lbs for me to get from 12% to 7%.

So that helps, thanks! Would like to get the precise formula for the future though if we can figure out what we are doing wrong.

 

[ella1985]

I was looking for the same question when came across to this thread. Now it's clear for me how to calculate how much weight to lose based on goal BF%.

 

[Hellawulf]

You need to get to about 168 pounds. Also take in consideration that at your size you may gain some muscle weight as you lose fat weight if you get on a good diet and workout. Good luck bro!

 

[Roofus]

You need to get to about 168 pounds. Also take in consideration that at your size you may gain some muscle weight as you lose fat weight if you get on a good diet and workout. Good luck bro!

Diet through the week is 95% solid. Gonna have to find the will power to put down the beer at the pool on the weekends and I wish my roommates would stop ordering that damn pizza! I can do it!

 

[shanarama]

There are body fat calculators out there, don't remember the sites specifically, but you can google it. You can plug in the numbers and it gives you the answer, it is just much easier than doing by hand. It is easy to track bf and lean mass that way as you go, so you get an idea of how much lean mass you are adding while cutting the bf. Just keep in mind that the bioelectrical impedence devices most people use to gauge bf have an accuracy of + or - 3% and your results will vary depending on how hydrated you are at the time you do the reading. You can get two very different answers if you test dehydrated vs. testing after consuming a liter of water....just had to point that out