Working out FG/ABV

[ADDLED]

Morning all, I barrelled my London ale this week. It started at 1.046 and finished at 1.016 after 5 days, roused and left for a day or two and still 1.016 so i racked it into a beersphere.

Thing is, I wasnt too happy with the OG when i started, but on advice decided not to add more DME to the FV. It tasted pretty good when i ran a pint off to heat up with the DME to prime, and so i threw caution to the wind and added a lot more than probably needed (200gms DME total and also approx 50gms light brown raw cane, now i remember) guessing that this will ferment out and increase the final ABV of the beer.

Recipe was 3kg pale LME and 250g of special grain steeped for 30mins. I also added a 500g bag of pale DME and the 200g of DME and 50g sugar to prime.


Is there a way I can work out what my final ABV might be?

Thanks!
Owen

[Jim]

Have a look near the bottom of this page. Bear in mind the footnote - some people use a lower constant.

Alternatively, this one does it for you.

[ADDLED]

Morning Jim, tks for the fast reply. Those tables are very handy and looks like I should have 4.9% ABV, maybe a bit less allowing for reasonable error margin.
Cheers!

[BlackBag]

Quick question Jim.
I noticed you suggested the Brew Calcs calculator. I've been using this one:
http://www.liquorcraft.com.au/wa.asp?id ... etails=106
How come there's so much difference in their results? Using Addled's example Liquorcraft has the result as 4.5% Whereas Brew Calcs comes out at 4.0%.
Am I missing something?

[Jim]

Quick question Jim.
I noticed you suggested the Brew Calcs calculator. I've been using this one:
http://www.liquorcraft.com.au/wa.asp?id ... etails=106
How come there's so much difference in their results? Using Addled's example Liquorcraft has the result as 4.5% Whereas Brew Calcs comes out at 4.0%.
Am I missing something?

Apparently, there's a bit of a fiddle factor required to work out ABV from OG, and different people use different fiddle factors.

[ADDLED]

Wow thats a big difference! Ive gone over mine again to see if i went wrong with me sums;

Liq. Extract : 3.000kgs x 300 potential / 23lts = 39.130
Crystal Malt : 0.250kgs x 240 potential / 23lts = 2.609
Dry Extract : 0.700kgs x 240 potential / 23lts = 7.304
Sugar : 0.050kgs x 370 potential / 23lts = 0.804
Total : 49.848 or 1.050

Ah!!! I didnt adjust for efficiency as i used liquid and dry extracts so there was no wort lost in mashing/sparging etc and nothing left behind in the boiler, so my calc would be 15% higher to start with. Was this correct?
Adjusting for temperature I got 1.052 OG and 1.016 FG giving 4.8%ABV. Using the Liquorcraft I got 5.0%ABV.

Jim does mention the footnote about constant (whatever that is ) and that it errs on the side of caution when calculating ABV.

So my beers a bit stronger than i thought... wot a bummer!