Originally Posted by RM-MN
Whoa! Lets back this up a bit. You want to bottle 5 gallons. To do that you need about 5.25 gallons into the fermenter because you will lose a bit to the layer of yeast you will leave behind. You will boil off a bit while you are boiling the wort, say maybe 1 to 1.5 gallons. (I lose less but I'm pretty good at controlling the boil) That means you need to have about 6 1/4 to 6 1/2 gallons before you start your boil. If you leave the trub behind you have to account for that loss. Why are you leaving it behind?
Well. My math for my OP sucked and I when I did it over again I found out that I have to multiply 5 gallon recipes it with 1.23.
And since I'm in europe. I did all my math in litres. I actually want to bottle 20L (5.3 gallons) juat because it's a nicer number, even though a cornelius keg is 19 litres, but I don't own any for the time being.
So working backwards:
Bottle volume: 20L (5.3 gallons)
Trub left in fermenter: 3L (0.8 gallons)
Into fermentor: 23L (6.1 gallons)
Lost to trub in boil kettle: 2L (0.5 gallons)
Boiloff and lost to cooling: 4.8 L (1.2 gallons)
Into boil kettle: 29.8L (7.9 gallons)
I actually forgot to take I to account that I need some trub (yeast) for bottle carbonation, so maybe there's a litre I should bring from the fermentor there.
There might also be some small numbers which didn't make it when I calculated from litres to gallons, but I think it's in the ballpark.
When I took a 5g recipe and multiplied everything with 1.23 all the numbers (OG IBU etc) were spot on in BeerSmith, and I could bottle 20 litres.