Dec 28, 2014 · And standard wall cabinets come 15″, 20″, 30″ and 40″ high and are 15″ deep. That means you can stack two 20″ high boxes next to a single 40″ and they actually line-up (unlike stacking two 15″ tall horizontals next to a 30″ wall cabinet and, well, you know… not so matchy!).