Help with Body fat percentage please!!!

So I want to know my body fat percentage because I am about to begin P90x and I would like to see how much fat I lose instead of weighing myself since.... Muscle weighs more than fat. I have tried online calculators but I don't know if I am doing it wrong.... So if anybody can help me calculate it and tell me how much body fat I have it will much be appreciated!!!!!

So these are my measurements....

Wrist: 6.1 inches
Waist: 32.5 inches
Hip: 37 inches
Neck: 13 inches
Forearm: 11 inches
Weight: 152
Height: 5'7

If you need any other measurements just let me know thanks!!!!