Wall Area Calculator - Net Paintable Area
Calculate net wall area from multiple wall dimensions minus door and window openings.
Walls
#1
#2
Doors / Windows (subtracted)
#1
Net Wall Area
156.0 sq ft
Gross Wall Area
176.0 sq ft
Openings
20.0 sq ft
How to Calculate Net Wall Area
Add each wall's length and height to get its gross area, then add each door or window's length and height as an opening to subtract. The result is the net paintable or usable wall area — useful for estimating paint, wallpaper, drywall, or siding quantities.
Example
Two walls — 12 ft × 8 ft and 10 ft × 8 ft — total 96 + 80 = 176 sq ft of gross wall area. Subtracting a 3 ft × 6.67 ft door (about 20 sq ft) leaves a net area of roughly 156 sq ft to paint or cover.
Common Use Cases
- Estimating paint or wallpaper needed for a room after accounting for doors and windows.
- Calculating drywall sheet counts for a renovation project.
- Figuring out siding material needed for an exterior wall with windows.
FAQs
Should I subtract windows and doors from the total?
Yes, for the most accurate paint, wallpaper, or material estimate — you generally don't need material to cover door and window openings. If you also plan to paint the door and window frames or trim, add a smaller separate allowance for those surfaces.
What if the net area comes out to zero?
A net area of zero means the total opening area you entered equals or exceeds the total wall area, which usually signals a data entry issue — double-check that your wall and opening dimensions are correct and in the same units.
Can I use this for multiple rooms at once?
Yes — just add a row for every wall across every room you're covering, and a row for every door or window throughout, and the calculator totals everything together into one combined net area.