If people sleep in the room, the window may have to work as an exit. Older houses often have a window that was fine when it was built and small by the rule a new permit uses.
Do not order from a blog
Clear opening size, sill height, and any well outside a below-grade window depend on the code edition the building department is applying. Ask that department, and have the contractor check the answer before anyone cuts the wall. This article will not print a size. A wrong size is a failed inspection.
Enlarging the hole is structural
A bigger opening can mean a new header. Ask whether an engineer is part of the scope. Ask who builds a window well and where the well drains, if the sill is below the dirt.
Who we are
Pane Pro SD refers a window contractor. We do not inspect for the city and we do not design the well.
Related: what to ask about a permit.