Convert from line to span

Unit Definition (line)
The line is a traditional unit of distance equal to 1/12 inch (about 2.1167 millimeters). For measuring the thickness of buttons, there is also a smaller line equal to 1/40 inch (0.635 millimeter). The line is called the ligne in French, the linea in Spanish, the linie in German, and the liniya in Russian.

Unit Definition (span)
Span is the width of a human hand, from the tip of the thumb to the tip of the pinky finger.