How to figure out ABV

I've been reading the instructions that came with my hydrometer as well as some different things online and I'm just a little confused right now.

I am currently fermenting a Czech Pilsner and it is my first brew. I did it from an extract kit that I got from my local home brew store. On the kit it says that the inital gravity is supposed to be around 1.05 and the final gravity should be somewhere around 1.015.

So this is a two part quesiton. My initial gravity was 1.041 after temperature correction. (I measured after I mixed the wort with the 3.5 gallons of water in the fermenter bucket and before I pitched the yeast) What did I do to be off by that .09? Is .09 alot to be off by?

Part 2, Does this mean that if I hit my final gravity of 1.015 the beer will be 3.4% ABV? To determine that I used the equation: (initial gravity - final gravity) x 131. If that is right it would also mean that if I had done the recipe correctly it would have been 4.5% ABV.

Thanks in advance for the help.

As long as you adding all of the Malt extract in the kit, you will be fine and around 1.050. Extract is known for having inaccurate original gravity readings. When you add the water, it doesn't seem to mix evenly and your hydrometer sample will be skewed. Sometimes higher, sometimes lower. But as long as you followed the instructions you will be hitting the right gravity. i would just use the 1.050 as you starting gravity for figuring out ABV

What brett said. As long as you didn't have any left over malt extract and you added the correct amount of water, it's hard to mess it up. I had the exact same concern in my first post over here.

To answer part #2. If you did manage to leave something out and your OG reading was correct, then yes, you would calculate your ABV with the lower number (and therefore have a lower ABV). But, like we said, it's unlikely you did that.

Temperature during specialty grain steeping can also effect O.G.

If the kit said that the OG should be 1.050, then it will be 1.050 assuming you made the right volume, and added all the wort to the fermenter.
Missing the gravity by .09 is a huge miss, but you only missed by .009. That's not so bad.
There are several readings why your gravity reading could be a bit off.
If you measured the gravity at a higher temperature than the hydrometer is calibrated to, then that will give you a slightly lower gravity.
Your hydrometer could be off by a few points. Check it in some cold water. If it reads a bit high or low, subtract or add the difference from 1.000 to all readings. i.e. if it reads 0.998, then add 0.002 to all readings.
The third, and most likely reason for you gravity reading is that you didn't mix the top-off water well enough with the wort. It takes an amazing amount of effort to get it thoroughly mixed.
Your calculations for determining the ABV are correct, but I would use the OG of 1.050 (assuming you ended up with the correct volume).

Congratulations on your first brew.

-a.

OK, I did add all of the extract and all of the wort into the fermenter. However this last post made me realize something. I didn't stir the wort when I added the additional 3.5 gallons of water.

I'm assuming it will mix in as it ferments?

The temp during the grain steeping was 160 I believe. I brough the water to 160, put the grains in and then took it off the heat for 45 minutes. That is what the recipe called for.

Thanks for the answers guys.

TimmyR41 said:

OK, I did add all of the extract and all of the wort into the fermenter. However this last post made me realize something. I didn't stir the wort when I added the additional 3.5 gallons of water.

I'm assuming it will mix in as it ferments?

Click to expand...

Yes.

TimmyR41 said:

The temp during the grain steeping was 160 I believe. I brough the water to 160, put the grains in and then took it off the heat for 45 minutes. That is what the recipe called for.

Click to expand...

Did you cool the wort before pitching the yeast?

TimmyR41 said:

OK, I did add all of the extract and all of the wort into the fermenter. However this last post made me realize something. I didn't stir the wort when I added the additional 3.5 gallons of water.

I'm assuming it will mix in as it ferments?

The temp during the grain steeping was 160 I believe. I brough the water to 160, put the grains in and then took it off the heat for 45 minutes. That is what the recipe called for.

Thanks for the answers guys.

Click to expand...

To assure a strong kick off to the fermentation process you need to airate the wort/spring water in you primary. Stir it in well, put the lid on it and shake it like a polariod picture.....then shake it again, then again, then again. THIS IS THE ONLY TIME YOU WANT TO OXYGENATE YOUR WORT. But, I wouldn't really worry about it to much about it now. Yeast know what to do. It might take them a little longer this time around to get started but they will eventually start to convert the sugars... and in the process the wort/beer will mix around.

yes, the wort was around 70 when i pitched the yeast.

next time i will be sure to stir the spring water/wort mixture before taking the gravity reading and pitching the yeast.

thanks.

I was ust reading the complete joy of homebrewing and found a contradiction. Just wondering which one is right.

In the book it says abc = (initial gravity - final gravity) x 105.

The formula I found on the Internet is the same but times 131 instead of 105. Which one is correct or is the one in the book a different equation and I'm reading it wrong?

TimmyR41 said:

I was ust reading the complete joy of homebrewing and found a contradiction. Just wondering which one is right.

In the book it says abc = (initial gravity - final gravity) x 105.

The formula I found on the Internet is the same but times 131 instead of 105. Which one is correct or is the one in the book a different equation and I'm reading it wrong?

Click to expand...

Probably he was referring to ABW (by weight). Different measure that isn't very common now.

http://www.rooftopbrew.net/abv.php
Quick and simple calculator that includes temp variants (the IBU calc is pretty good too).

passedpawn said:

Probably he was referring to ABW (by weight). Different measure that isn't very common now.

Click to expand...

Yes, he actually says by weight in the book.

-a.

TimmyR41 said:

I was ust reading the complete joy of homebrewing and found a contradiction. Just wondering which one is right.

In the book it says abc = (initial gravity - final gravity) x 105.

The formula I found on the Internet is the same but times 131 instead of 105. Which one is correct or is the one in the book a different equation and I'm reading it wrong?

Click to expand...

abc?

(OG-FG)*131 is an approximation of ABV, but it's not very accurate with bigger beers. For instance, I have a beer that was a 1.108 OG and a 1.031 FG; the easy formula says it's 10.1% ABV, but it's actually closer to 11.4%.

The more accurate calculation is:
abw=76.08*(og-fg)/(1.775-og)
abv=abw*(fg/.794)

j1laskey said:

To assure a strong kick off to the fermentation process you need to airate the wort/spring water in you primary. Stir it in well, put the lid on it and shake it like a polariod picture.....then shake it again, then again, then again. THIS IS THE ONLY TIME YOU WANT TO OXYGENATE YOUR WORT. But, I wouldn't really worry about it to much about it now. Yeast know what to do. It might take them a little longer this time around to get started but they will eventually start to convert the sugars... and in the process the wort/beer will mix around.

Click to expand...

If you are topping off with 3.5 gallons of bottled water / spring water there is plenty of dissolved O2 in it so you really don't need to worry about aerating your wort. When you do full volume boils it becomes much more important because most of the oxygen dissipates out during the boil.