SIZE m_sizeExtent;
Remarks
The extent of the control in HIMETRIC units (each unit is 0.01 millimeters) for a particular display. This size is scaled by the display. The control's physical size is specified in the m_sizeNatural data member and is fixed.
You can convert the size to pixels with the global function AtlHiMetricToPixel.
CComControl Overview | Class Members
See Also CComControl::m_sizeNatural, CComControl::m_rcPos, SIZE