How can these figures be So differently

So I have been using a refractometer on brew days and hydrometer to check final gravity. But today I used the refractometer calculator on our website to give it a whirl. So here is what I got between the two readings.

English bitter: OG taken with refractometer 12 brix (1.048), FG taken with hydrometer 1.014 = 4.5%

English Bitter: OG taken with refractometer 12 brix (1.048), FG taken with refractometer. (5.25)

and with the calculator above: OG of 12 brix, FG is 5.25 = 1.004 @ 5.884% 1.3% more in abv and 10 points lower in gravity.

I just don’t get it. I know my hydrometer could be off, but 10 points? and I don’t think I could get a beer anywhere that low with S04. It was mushed @ 150F but come on.

I would assume that calculator uses an out dated formula.

Try Sean Terrill’s Calculator and see what you get. He has spent a lot of time creating a better refractometer final gravity formula. ... alculator/