Convert from button measure to pie [Spanish]

Unit Definition (button measure)
The button measure is a unit of distance equal to 1/40 inch (0.635 millimeter), used to measure the thickness of buttons.

Unit Definition (pie [Spanish])
The pie is a traditional foot of Spain. The pie equals 1/3 vara or 12 pulgadas. The pie used in Spain is about 27.86 centimeters or 10.97 inches, but in Spanish Latin America the pie is generally longer.