Convert from button measure to tu

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 (tu)
The tu is a traditional Chinese unit of distance equal to 250 li. Using the late nineteenth century definition of the li as 2115 feet, the tu was equal to 100.14 miles or 161.13 kilometers.