ABV Calculations. Each to Their own?

[Bill Berry]

Hi everyone,

At the risk of going over ground which may have been covered on this forum (many times?) before I was wondering if there is a standard UK method of abv calculation.

I used to use the ...divide by 7.36 method but started to notice discrepancies with other data when I started looking at Brix conversion and refractometry. It seems that the Americans tend to adopt the 'multiply by 131' or '135' approach.

I understand why these variations occur but just out of interest I was wondering if it is a case of 'each to his/her own', or if there is a standard UK approach to such calculations?

Cheers!

[lockwood1956]

The most widely used calc in the UK is the one you have been using, but none of them are 100% accurate....just a guide

[NorthernWiner]

I actually prefer the Brix scale over SG. I find it much easier to use (for a number of reasons).

To calculate ABV, I multiply degrees Brix by 0.57 (some use 0.55).

So, for example, must at 24 degrees Brix would produce alcohol in the 13.7% range.

[Bill Berry]

Thank you both for such speedy responses!

This leads me on to two other questions...

Firstly, is there a standard abv calculation for bottles of wine sold here in the UK or is commercial abv description solely down to the producer?

Secondly, I assume, Steve, that you use a refractometer and the Brix calculation is made on the assumption that the wine will ferment right out. Is it easy to calculate the abv using your method if the batch fails to ferment right out? How do you calculate the abv if this unfortunate event befalls your batch? (I only ask as stuck/stopped batches have happened to me a couple of times... )

[NorthernWiner]

Bill, I use a refractometer along with a spreadsheet that compensates for ethanol. So, even if it sticks, I know the current Brix level and can still calculate ABV based on starting/ending Brix.

The spreadsheet can be found here:

http://morewinemaking.com/public/wine/Wine_refract.xls

I should add that I often use a narrow range hydrometer when the sugar gets close to zero. At that point it's difficult to read the refractometer because the alcohol causes some fuzziness in the viewer.

[Bill Berry]

Thanks Steve,

I haven't got a refractometer yet but I'm toying with the idea. The spreadsheet will be very useful.

Thanks again,

All the Best,

BB

[cpfan]

Bill:

dividing by 7.36 is roughly the same as multiplying by 135.6.

To make things simple, I will use starting sg 1.095 and ending sg .995. Diff is .100

factor 131 yields 13.1%
factor 133 yields 13.3%
factor 135.6 yields 13.56%
division by 7.36 yields 13.58%

If you like to have a high alcohol wine use the higher factors. Personally I would just say it's around 13% to 13.5%.

Steve