Like OlivierF says, in the US, an architect's scale has scales of 1 foot equals 3/32", 1/8", 3/16", 1/4", 3/8",1/2", 3/4", 1", 1-1/2", and 3". These translate to 1:128, 1:96, 1:64, 1:48, 1:32, 1:24, 1:16, 1:12, 1:8, and 1:4. An US engineer's scale has scales of 10, 20, 30, 40, 50, and 60 feet to an inch. These translate to scales of 1:120, 1:240, 1:360, 1:480, 1:600, and 1:720. If you're working in any other scale, go metric. I remember in the 70's the US was going to go metric. I don't know what happened but the only use of metric currently is for alcoholic beverages. Of course, you do need metric wrenches to work on any recent car or bicycle. Fair winds!