I don't think that the caliper pinch is nearly as accurate as the hydro testing. The pinch test has so many variables and is an average of different body parts. I would go to your hospital or your local university kiniesiology department and get the dunk test if you want something that is bang on. If you want something pretty accurate but not exact, use a BF% scale, then thirdly use the pinch test or a calculation based on different body measurements that can be found here:
Let me know if you need any help. It might be a percent or two off but will definitely give you a number to work from.
Good luck. Ben