Gets the height and width, respectively, of an object.

dimension = MyObject:GetWidth();
dimension = MyObject:GetHeight();

Returns Edit

dimension 

Number - height/width of the object in pixels, in its own coordinate space (scaling dependent). This is the desired height/width, if set with :SetHeight() / :SetWidth(), or the actual height/width used if computed from two or more :SetPoint() calls.

Example Edit

myAddonOptionsParent = myAddonOptions:GetParent();
myAddonOptions:SetHeight(myAddonOptionsParent:GetHeight() / 2);

Result Edit

The frame named "myAddonOptions" would be set to half the height of its parent frame.

Notes Edit

Note that even though FontString has GetWidth()/GetHeight() methods, they behave very differently and have potentially very little to do with the displayed dimension.