Body Fat %

Whats up Tmen/vixens I was wondering if those body fat calculators that you find online are even close? You know the ones where you choose male or female then put in your waste size and weight. Also on another note I was just interested to know how those of you who have used hammer strength equipment liked it? I worked out on it for the first time earlier this week and really enjoyed it. By no means am I ready to replace free weights with it but I found it to be a nice alternative. Anyways, let me know what you think about the body fat calc and hammer strength. Thanks.