8K Square feet... I guess that'll do it. I didn't think till afterwards also, depends highly on what woods you've got available to burn too. Guys that are predominantly in softwood territory are going to burn a lot more to get the same heat as people that have access to good hardwoods.
If there is anything I could call lucky about living where I do, it's easy access to some of the really good hardwoods. Hickory, White Oak, Black Birch, Locust... all plentiful here, have lots & lots more BTU's available per cord than softer/lighter woods.
Kind of a strange irony, the further north into the deep cold that you get, the softer/lighter most of the wood supply is.