Convert from feet [international, U.S.] to pes

Unit Definition (feet [international, U.S.])
The human foot has long been a standard unit for the measurement of length. Over history this size has varied from region to region and there is some discrepancy as to an exact standard or origin of the standard measurement for feet that we use today. In England, the Roman foot was replaced after the fall of Rome by the natural foot. The modern foot (1/3 yard or about 30.48 centimeters) did not appear until after the Norman conquest of 1066. It may be an innovation of Henry I, who reigned from 1100 to 1135. Later in the 1100's a foot of modern length, the "foot of St. Paul's," was inscribed on the base of a column of St. Paul's Church in London.

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.