Calculate weight based on body fat percentage This is the YMCA method for determining body fat percentage for a female based on weight and waist size: $${-76.76+(4.5A)-(0.082B)\over B}=C$$ Where: A = Waist size in inches, B = Weight in lbs, C = Ratio of body fat. I would like to re-arrange this formula to solve for B. ie: determine target weight based on waist and body fat ratio. Source: < Thanks in advance! :-)

Cross multiply:

$$-76.76 + 4.5 A - 0.082B = BC$$

Rearrange:

$$-76.76 + 4.5 A = 0.082 B + BC$$

$$-76.76 + 4.5 A = (0.082 + C)B$$

So:

$$B = \frac{-76.76 + 4.5 A }{0.082 + C}$$