Exactly how accurate are body-fat measuring scales?

I recently bought myself one of those body-fat measuring scales, stepped on it and it showed me a reading of about 6-8% body fat. I am 17 years old, male, 5'10, 136 pounds just for the record. I am wondering how accurate is that reading?

Public Comments

1. I believe that most heavy weight boxers score as clinically obese, but none of the people who invented the scales go to boxing matches to tell Mike Tyson etc that they are obese. I wonder why. I'm pretty similar in weight and height to Frank Bruno in his prime. That doesn't make me Frank Bruno in his prime. The scales have on totally accurate measurement, how much you gave someone else to own them. It's called a price tag. And don't feel insulted, you should see some of the gadgets I've bought.
2. calipers - crappy buoyancy - good electrical impedance - great