4x8 U-Haul Cargo Trailer Dimensions: Inside dimensions: 8'8" x 4'6" x 4' (LxWxH) Door opening: 3'6" x 3'9" (WxH) How much can you fit in a 4x8 U-Haul Cargo Trailer? Let’s find out. It’s the perfect size for a college dorm or a small loft. You can also use it for all sorts of home projects. #UHaul #Trailer #Towing #MovingTips #UniLife Find all listed towing vehicle requirements on our website.