Electrical enclosures come in a wide range of sizes to accommodate various applications, from small 75 x 125 x 35 mm boxes for compact setups to large wall-mounted units measuring up to 1200H x 1200W x 400D mm for more extensive installations. Electrical enclosure sizes are not universal, but most manufacturers follow common size families. This guide explains typical wall-mount and floor-standing dimensions, how to read catalog sizes, and how to choose the right enclosure size for your layout. Choosing the correct electrical box size is important for safety, proper wiring installation, and compliance with electrical codes. Electrical boxes. Large electrical power distribution boxes come in several sizes—single-gang for one device, double-gang for two, and so on. They help keep everything inside safe and working properly. Picking the right size matters. Your purchase of these products through.