Refractometer / Brix - Final Gravity

Hey all.

I found this site: http://onebeer.net/refractometer.shtml

It says it does the math to convert same-temp/accurate brix measurements from a refractometer to gravity readings.

I am (and have been) using a refractometer to avoid beer waste. A few drops >> filling a hydrometer.

My question is, is this site accurate? I frequently get a starting brix around 15-17, and my finals are around 5-8. That would indicate some seriously high alcohol by volumes using this calculator. Not that I mind at all, just wondering if the calculations on the above site are correct for 68°F wort measurements.

I'm in search of the correct conversion too.
Do you get repeatable measurements with your refractometer? During my brew yesterday, I was getting very different readings from the same wort under the same conditions.

Here's a site that has a conversion table that appears to use the same calculation as the one you referenced:
http://www.winning-homebrew.com/specific-gravity-to-brix.html

Mine seem to be consistent, yes.

Using roughly the same amount of grain/boiltimes/water I am getting roughly the same readings across multiple brews at roughly the same temps.

I am just not sure if the ABV%'s I am seeing using this tool online are accurate...