The size of the returned bounding rectangle is influenced by the type of end caps, pen width, and pen miter limit, and therefore produces a "loose fit" to the bounded path. The approximate formula is: the initial bounding rectangle is inflated by pen width, and this result is multiplied by the miter limit, plus some additional margin to allow for end caps.

Namespace: System.Drawing.Drawing2D
Assembly: System.Drawing (in System.Drawing.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0