Typically, the industry standard 55-gallon steel drums utilized for shipping, storing or containing liquids or hazardous materials are about 22.5 inches wide by 33.5 inches tall. However, some designs might be taller and narrower. Commonly available 55-gallon plastic barrels are about 23 inches wide by 35 inches tall.
The dimensions of 55-gallon barrels derive largely from standards set by the U.S. military during the Second World War. These dimensions allowed four drums to fit tightly and easily onto a typical wooden pallet. Through the use of forklifts, this greatly increased the ease by which drums could be transferred between shipping containers or vehicles.