Sugarless, here are a few you can choose from. Your best bet is to use one over time and go with the general trend - they are all just estimations at best and can be off by quite a bit.

http://www.linear-software.com/online.html
http://www.healthcentral.com/coolto...ss/bodyfat1.cfm
http://www.users.voicenet.com/~petr...ss/ckdcalc.html

Cheers,
Nat