Use actual panel width
Manufacturer panel width—not a generic nominal bay—should control panel count.
Short end bays may require cutting only if the selected system permits it.
Classify posts
Line, corner, end, gate, transition, and blank posts can have different routs or reinforcement.
Count them from the plan rather than applying one post SKU everywhere.
Lay out gates separately
Gate openings change adjacent post types, hardware, reinforcement, and panel run length.
Use the gate kit's required opening and installation instructions.
Count system accessories
Rails, brackets, caps, stiffeners, inserts, fasteners, and transition components depend on the chosen product family.
Use the manufacturer bill of materials where available.
Check site requirements
Grade, post embedment, frost, wind, utility locations, property lines, pool barriers, and permits can change the installation.
The quantity takeoff is not a substitute for local requirements or manufacturer instructions.