Body Fat Calculators?

Ok. So my question of the day is "Is there any body fat calculator out there that is accurate?" I dont have insurance and money is tight so going in some where to figure it out with a professional isnt possible. I know there's a ton online. All of them asked for measurements; some with more than others. All of them gave me drastically different answers though. Ones that included wrist size, forearm, calf, and thigh size were almost 20% lower than the ones that asked for height, weight, waist and hip measurements. Can anyone enlighten me a bit?