Convert from button measure to block [East U.S.]

Unit Definition (button measure)
The button measure is a unit of distance equal to 1/40 inch (0.635 millimeter), used to measure the thickness of buttons.

Unit Definition (block [East U.S.])
The Block is an informal unit of distance popular in the U.S. A block is the average distance between street intersections in the rectangular street grids common in most American cities. The length of a block in Eastern USA is about 1/20 mile or 80 meters.