So you have to lose 1.5 pounds of BF to lose 1%.....I think your asking what % of the w8 you lose is BF....the answer is that it 'varies'..and it is possible to gain LBM at the same time....so you may on occassion lose 2 pounds of BF and gain 2 pounds of LBM...and the scale doen't move!
Solution is to take skinfolds....and BW...let us do the math
Yep, a percent means a portion of 100, meaning you must divide your own bodyweight.
Each additional percent will be with a new weight in mind, since your bodyweight will change from the first time. Or to keep it simple just keep track of your bodyweight and bodyfat % every 2-4 weeks to track progress, remember that all weight loss isn't a good thing so definately get some calipers if you don't have them already. Water, muscle, bone, fat, all has weight and some people (especially women) seem to think that any kind of weight loss is good and must be fat.