More ideas from I
Furniture dimensions don't come out of the air. They come out of heavy research that, thankfully, a lot of people have already done for us and written books on; if you're a designer, you ought have a copy of one of these books (see bottom of this entry). While these

Some basic ergonomics rules that makes the furniture compatible with the user (Seating Designers Secrets: Common Dimensions, Angles and Heights).