Goal Body Weight Calculator

So I started working with a new trainer this week and one of the things we discussed was what goals I want to reach. My original goal was to reach 190 pounds by 11/1. After we had checked my BF%, he strongly suggested that I look at using that as my goal. Who knows what a good number that would be though. In a perfect world I would love to get down to 15% at the end of my journey, which is 1/2 of my current level.

We used the calculators here - http://www.fat2fitradio.com/tools/ - to verify current BF% that we had received on the hand held machine.

Using the goal weight calculator, we came up with the following numbers, I am now just trying to see if it is realistic.

You currently weigh 258 pounds with a body fat percentage of 29.8%. You would like to have a body fat percentage of 15%.

Based on this information, your goal body weight should be: 213 pounds

How did we calculate this goal body weight?

We took you current weight and your current body fat percentage and multiplied them together. (Weight X Current Body Fat %/100) to get how many pounds of you is actually just fat. In this case you are currently carrying around 77 pounds of fat. To get your goal body weight we work backwards and divide your lean body mass by one minus your goal body fat percentage. (Lean Body Mass / (1 - Goal Body Fat %/100). This calculation yields your goal body weight.

When you reach your goal, hopefully you have maintained your current lean body mass of 181 pounds.

So can other people who are at or near goal let me know if this is realistic?