Does volume affect gravity?

So, I made a Munton's Nut Brown Ale extract kit. Based on the instructions on the kit, it's for a 6 gallon batch. It indicates a starting gravity of 1.040 to 1.044 and a final of less than 1.012. I brewed a 5 gallon batch based on my homebrew store's instructions and had a starting gravity of 1.054 and have been consistently at 1.020 for several days.

My question is, since my starting gravity was approximately 0.010 higher, should I expect my final gravity to also be 0.010 higher or should it still be below 1.012?

Any help is appreciated! Thanks...

Total Gravity

http://beerglossary.com/index.php?title=Total_Gravity

The kit, designed for 6 gallons, would have a total gravity of

6 gallons X 40 gravity units = 240 total gravity


Gravity units are found by taking the last two digits of the SG (unless it's 1.100 or greater, you get the picture). So, if we made the same kit using only five gallons, we can use the formula backward.

240 TG / 5 gallons = 48 gravity units

So, the same sugar in 5 gallons would give you an OG of 1.048. Total Gravity never changes despite volume. Since you made it up to 1.054, you might have boiled lower than 5 gallons, or there could have been more sugar than was predicted.

You can use TG for the FG too.


6 gallons X 12 gravity units = 72 total gravity

72 gravity units / 5 gallons = 14ish

So, with the same kit in 5 gallons, expect around a 1.014 for the FG, assuming the gravity hit properly (but yours was high). Give it more time, perhaps. 1.020 sounds a little high yet for a brown starting around 1.054. Of course, if it stays consistent, finish it up.

Curse of 1.020 strikes again... The yeast in that kit isn't great. You might be stuck at 1.020. Give a gentle swirl and raise the temp to 70-74. That might wake the yeast up to finish the job. Or you may just be left with a bunch of unfermentables. Remember the math lesson above though it comes in handy. But instead of following that method for FG look at the yeasts apparent attenuation and grab the calc for estimating FG based on the oG and attenuation to guess at what that number should be.

Draken said:

But instead of following that method for FG look at the yeasts apparent attenuation and grab the calc for estimating FG based on the oG and attenuation to guess at what that number should be.

Click to expand...

Yup. The part I showed you was the science. What Draken is suggesting is the art. In practice, beer flows much easier by embracing your artistic side (just so long as you understand the science). Trust your senses, including the common one.

Give the swirling a shot to see if you can squeeze out a few more points, then leave it to clear and bottle it up.