I need to paint my great room - hall - and dinette. Its all painted the same color. I measured (three walls have those tall vaulted ceilings) -- but as best I can tell - the area measures 1441 sq.ft. I have thrown away the sales slips for the paint we bought - years ago - and I have no idea how many gallons. It will be flat paint, as close to the original color as possible. Hopefully, one coat will cover it. How many gallons do I need? My late husband always bought the paint - well, I bought it, but he told me how many gallons to buy. Any help would be appreciated. Will probably shop at Home Depot or Lowes. Thanks.