Finished measurements are the measurements of the sewn garment, not of the body. The difference between the two is the ease.
You can measure finished measurements straight off a digitized pattern, because the file is to scale in millimetres. That is the fastest way to tell whether a pattern will actually fit before cutting.

Digitize sewing patterns without tracing.
Test PatternScan Pro free for 14 days with the full feature set. You need your smartphone, a printer and one pattern you always wanted digital.