Body Fat Percentage Calculator?

DEXA, bod pod and hydrostatic weighing are the most accurate, but also fairly expensive. (I lie, dissection is the most accurate, but, you know...).

Calipers are the next most accurate, if used correctly. I think they're pretty hard to use on oneself.

Tape measure + formula (like those websites above) aren't bad, but the formula is based on a bunch of averages from different people, so your results may vary.

The BIA scales (Bioelectrical Impedance Analysis) are easy to use, and they tend to be /precise/, but not /accurate/. What that means is that the total bodyfat number they give you can be way, way off, but if the number changes, that probably does reflect a real change in your bodyfat. The other thing to keep in mind with BIA scales is that the results vary based on how hydrated you are at that moment. They give best results when you use them right when you get up in the morning, since you're likely to be similarly hydrated from day to day at that time.