I think I recall that others have said that it works for 10gal brews also but I guess it also depends on the OG you want. They recommend buying this because you could also do 10 gal if you wanted to. I mostly do 5 gal brews but I opted to get the 10gal. 5 gal brews, IIRC it is less than half way brew for a 1045 brew.