I wrote these equations out if anyone would like to use them.
(x-lean body mass)/x=decimal percent desired BF%
This will give you your goal weight assuming you don't put on muscle. If you anticipate adding 5-10 lbs of muscle over a certain period of time, adjust your lean body mass accordingly. If you believe you're going to lose muscle, for example 20% lean tissue per pound muscle lost, you have to subtract that from your lean body mass.
172 = current body weight
129.21 = rough estimate lean body mass
18% = desired body fat percentage
[x-(129.21-(172-x)*0.2)]/x = 0.18
<Goal Weight Assuming Lean Body Mass Held Constant>
@ 20% BF
(x-129)/x = 0.20
172*0.25-161.25*0.20=10.75 lbs fat lost
@ 18% BF
(x-129)/x = 0.18
172*0.25-157.3*0.18=14.69 lbs fat lost
Here's a link to an online equation solver. Hope someone finds these handy!