Outside measurments of standard Langstroth boxes made of 3/4" stock are 19 7/8" by 16 1/4". The rabbet is typically 5/8" deep and 3/8" wide. The eight frame box is the same 19 7/8" and the same rabbet. But the width actually varies. The only two commonly sold sizes (unless you order from Western Bee Supply who will make them whatever you like) are 14" (from Mann Lake and Betterbee) and 13 3/4" (from Brushy Mt. and Miller Bee Supply). Mine are all 13 3/4". Full plans are available for all the ten frame equipment on Beesource.
For internal dimensions, subtract 1 1/2" (3/4" times 2) from width and length. Depth stays the same, of course. 11 5/8" for Dadant deep, 9 5/8" for Langstroth deep (although many cheat it down to 9 1/2" now), 6 5/8" for mediums (Illinois) and 5 3/4" or 5 11/16" for shallows and 4 3/4" or 4 11/16" for extra shallows.