Convert from pes to gnat's eye

Unit Definition (pes)
The pes is the Roman foot, equal to 29.67 centimeters (about 11.68 inches). The pes was divided into 12 unciae (inches). There were 5 pes (or pedes) in 1 passus (pace, see above), 10 in a decempeda, 625 in a stadium, and 5000 in the Roman mile.

Unit Definition (gnat's eye)
The gnat's eye is an idiomatic "unit" of distance; it's common to hear that something is "as small as a gnat's eye". In fact, the eyes of typical gnats tend to have diameters similar in size to a hair's breadth: roughly 100-150 micrometers (0.10-0.15 millimeters).