Convert from button measure to Q

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 (Q)
The Q is a metric unit of distance equal to exactly 0.25 millimeter (9.8425 mils) used by typographers and page designers in Japan, in Germany, and in other countries in preference to the traditional point. One Q is equal to about 0.71 point, a little more or less depending on the exact definition of the point. This unit is also spelled kyu.