how much beer in 3 gallon carboy?

[Arbe0]

just measured my 3 gallon carboy: the carboy weighs 9.94 lb and a of water weighs 8.34 lb. So one gallon in my carboy weighs 18.28 lb. with one gallon in it. 2 gallons is 26.62 lb and 3 gallon is 34.96 lb. The 34.96 gallons of water goes all the way up to the opening in the top of the carboy. this means that I should only do a 2.5 gallon fermentation in a 3 gallon carboy, maybe just a little more if I am brave and have a good blow off tube on.
To look at it by inches from the outside of the carboy: the bottom is approximately 1 inch thick (not counting that bump on the middle of the bottom)from the floor (outside the carboy) to the one gallon water mark is 5 inches. so every gallon is 4 inches and every half gallon of water is 2 inches.

 

[DBhomebrew]

Is there a question?

 

[Yesfan]

Not sure what your asking but.......

In a pinch, put a strip of masking tape from top to bottom of your carboy. If you have a half gallon pitcher, pour a half gallon of water in your carboy and mark the location. Repeat with every half gallon until you get to the top. Make note of the 2.5 gallon mark as your max volume for fermentation. Take the accumulated water and use it for your next 2.5 gallon batch of beer.

 

[Kickass]

Weight is a great way to verify volume.

 

[IslandLizard]

The 34.96 gallons of water goes all the way up to the opening in the top of the carboy.

I'd say it goes way over the top...

 

[lumpher]

Ouch... all that math with no question makes my mug hurt. Maybe I need to fill it up with some cold soothing liquid.

 

[Arbe0]

Ouch... all that math with no question makes my mug hurt. Maybe I need to fill it up with some cold soothing liquid.

Sorry. No question just thought it would be good for there people to know.

 

[IslandLizard]

Sorry. No question just thought it would be good for there people to know.

Thank you, it's a valuable reference for those not wanting to do the math.

Just a general word of caution, be very, very careful handling glass carboys.

Being (large) glass vessels, they can break, often unexpectedly, due to shoddy manufacturing standards and lack of QC, or even a mere misplaced bump. The 3 gallon ones may be a bit safer to handle than 5 or 6 gallon versions due to holding less volume/weight. Still be very cautious and aware of potential risks, and protect yourself.
To illustrate the dangers, we have a compendium on broken carboys, be forewarned, it contains some grim encounters.

Before i became aware of those risks I used to shake 6 gallon glass carboys in my lap for aeration and when cleaning. I was not wearing a welders apron, just jeans or shorts. What was I thinking?

There are good (better?) plastic alternatives, as well as stainless ones.