Use a siding removal tool.
Cutting siding away to remove an exterior windows.
Slip the curved end of a vinyl siding zip tool into the seam between two horizontally interlocking runs of siding that you need to remove.
Remove the pieces of vinyl siding from around the window area.
Then subtract that amount from the length of the piece of siding you re going to cut.
Wedge the pry bar under the trim.
Extract nails keeping the vinyl pieces in place in order to prepare vinyl pieces to be removed.
Measure the length of the section of wall you re covering with siding.
Use this tool by inserting it where a piece of vinyl overlaps a piece below it and then sliding it across until you reach the end of the piece.
Work the pry bar along the entire length of trim.
Do not cut the vinyl off.
Caulk the new one in using some good urethane sealant and hope that it never fails and that water never gets behind the siding at any point above the window.
You can also cut the siding back far enough to reach the flange and then install new trim around the new window.
Remove all the trim from the wall having the siding replaced.
The total you get is how much you ll need to cut off the siding.
Use measuring tape to measure how much siding you need to cut off.
The third option is to cut between the side of the window frame and the edge of the.