Calculating Attenuation

[NRB]

Gents and lady,

I feel stupid asking this as maths was a strong point when I was at school, but I've been trying to calculate my yeast's (SAFale S-56) apparent attenuation in my first AG brew. I've searched the forums, but can't find an answer.

According to JJ Palmer, apparent attenuation can be calculated by the following formula:

(From FG = OG - (OG X %att)
* %att = (OG - FG)/OG)

My figures (with the beer sitting in secondary) are:
OG 1062
FG 1009

%att = (1.062-1.009)/1.062
%att = 0.053/1.062
%att = 0.05

This is obviously incorrect, but where am I going wrong?

I plugged it into a java based online attenuation calculator (I found via Google) and it came out at 84%

I feel so damn stupid right now. :unsure:

 

[tdh]

Hi NRB.

you need to drop the 1 and the decimal point from the SG reading, multiply by a thousand to get whole numbers then -

62 - 9 = 53

53/62 = 85.48387%

tdh

 

[tdh]

Bloody high attenuation by the way!!!

With the 53 point gravity drop you can get a rough idea of ABV.

53 x 0.13 = approx. 6.89% alcohol by volume.

Phew! Big beer!!!

tdh

 

[NRB]

Thanks for clearing that one up tdh - it's not particularly clear in the text.

As for it being a big beer - yeah.. not what I was expecting. My fist AG was MEANT to be an APA, Sierra Nevada Pale Ale initially, but I guess my efficiency was a lot higher than that of the recipe creator. A link to my recipe is found here.

I discovered I hadn't put any loss details into Promash and had 5L in the kettle after draining to my fermenter, so I decided not to top up and pitched as it was.

Initial tasting after 2 weeks in primary as I racked showed it to be very malty in flavour and reasonably bitter. It gives a twang down the sides of the tongue late. I'm hoping it'll become nice with age, but given the ABV I've come out with, I guess it's definitely going to need a little aging to enjoy. It's not as expected, but being an AG virgin and flying by the seat of my pants, what can one expect??

Is there any empirical information of ABV calculation? How To Brew is as you've stated, change in gravity x 0.13, but Liquorcraft Brew logs use 0.14. Liquorcraft also claims 0.5% increase with priming sugar, I actually thought it was lower, approx 0.3%

Chees and thanks again!

Nick