As of July 2015, lumber size charts are at websites for The Family Handyman, The Old Farmer's Almanac and Rempros. The Handyman website has a chart showing the actual dimensions of boards identified by specific thicknesses or widths. For instance, a 1-inch thick board is really three-quarters inch thick.
The Almanac website has two lumber dimensions charts. The first displays the actual size of dry or seasoned wood compared to its nominal, or named, size. The second shows the board feet measurement, or cubic size, of lumber.
Rempros has separate charts for softwoods, such as pine, spruce and fir and hardwoods, including oak, maple and walnut. Each chart indicates the real size, in inches or millimeters, of several lumber dimensions.