How big is this 20yard dumpster? The approximate overall dimensions of a 20-yard dumpster are: 18 feet long by 8 feet wide by 3 1/2 feet high, and 2 1/2 feet high on the inside of the bin. Please see the dumpster dimensions graphic, below. The AMD dumpster will typically fit in a standard residential driveway, however, only if the street access is adequate.