Here's the formulas I use. NOTE: These only work for men...So, they probably won't be of much use. I have them all preprogrammed into a spreasheet. I just punch in my weight and waistline each week and it tells me what my fat weight and lean weight are; how much weight, fat weight, and lean weight I've gained/lost since last week and since starting; what my average weekly wt/fat/lean gain/loss is; what my body fat percentage is; an estimate of what my BMR is; who many Calories minus those burned in exercise I'd have had to have taken in for the Calorie theory to be correct; and what my weight and waistline would be at various body fat percentages assuming no change in lean weight.

lean = ((wt*1.082)+94.42)-(waist*4.15)
fat = wt - lean
adjusted weight = wt-(lean-(iw*0.85))
bf% = (fat/wt)*100
true ideal weight = lean/(1-(ideal bf%/100))
bmr = (wt-(iw*(1-(ideal bf%/100)))+wt)*10
kcal = bmr+(((Δfat*9*454)+(Δlean*4*454))/7)
waist [at a given wt] = (lean-94.42-(wt*1.082))/-4.15
weight [at a given bf%] = lean/(1-(bf%/100))

wt = weight
iw = ideal weight according to the height-weight charts

In fact, I actually have draw graphs of each of these...So, I don't even have to look at the numbers themselves, just the graph.