2010 ADA Standards for Accessible Design Pocket Guide

703.2.5 Character Height.

Character height measured vertically from the baseline of the character shall be 5/8 inch (16 mm) minimum and 2 inches (51 mm) maximum based on the height of the uppercase letter “I”. [S.H. 4.30.4]

EXCEPTION: Where separate raised and visual characters with the same information are provided, raised character height shall be permitted to be ½ inch (13 mm) minimum.

Figure 703.2.5 Height of Raised Characters