Accurate Brix measurement. Which one is right?

Brewpal tells me 5% ABV
NB tell me 7.8% ABV
Read on:


I use Brewpal as well as Northern Brewer's refractometer calculator http://www.northernbrewer.com/refractometer-calculator/ to measure Brix. You would think the numbers would come out the same but I'm getting two numbers. Unfortunately my refractometer only reads in Brix but I would still like to see where I'm at post fermentation. ABV and Final gravity.

Most recent brew (Saison):

OG 14.80 Brix
FG 6.00 Brix

Data according to Brewpal:

14.80 Brix down to 6 Brix = 5%
Or
1.063 down to 1.025= 5% ABV

Data according to Northern Brewer's During and After Fermentation calc.

14.80 Brix down to 6 Brix = 1.001 FG

Data according to Northern Brewer's ABV calc.

Current Brix 6.00
Current Gravity 1.001
ABV 7.872
OG 1.06

Any ideas why they are different? A fault in an algorithm somewhere?

Remember that alcohol changes light refraction, so the reading of FG is useless. There are some conversion software calculators out there that may be in the ballpark (lots of people like Sean Terrell's), but I've never found one that is accurate.

You can always take an OG reading and convert it to the SG scale, but not a FG reading.