Understanding your result
Net surface area is the room surface before extra layers or waste. Purchase coverage includes both adjustments. The sheet count rounds upward once across the combined area.
After planning the wall lining, estimate the finish with the Paint Calculator .
The formula
Every wall is counted once around the room perimeter. Ceiling area equals length times width. The quantity is an area-based estimate, so it assumes usable offcuts can be shared between surfaces; it does not generate a cutting layout.
Worked example
A 5 m by 4 m room with 2.5 m walls has 45 m² of wall surface. Deducting 4 m² of openings and adding a 20 m² ceiling leaves 61 m². One layer and 10% allowance need 67.1 m², or 24 sheets measuring 2.4 m by 1.2 m.
How to use this calculator
- Enter the inside room dimensions and choose whether to cover the ceiling.
- Deduct relevant wall openings and enter the actual sheet dimensions.
- Set the number of layers and allowance before reviewing whole sheets.
Sheet orientation can change an order
Equal sheet areas do not guarantee equal installation layouts. Wall height, sheet length, framing positions, joint staggering, and access restrictions determine how panels can be fitted. This estimate pools coverage; inspect a panel layout before purchasing where long narrow pieces or unusable offcuts are likely.
Openings and additional materials
A window removes finished surface area, but installers may cover and cut around it rather than reuse every offcut. Deduct only the openings appropriate to your estimating method. Tape, compound, fasteners, corner bead, adhesive, and primer depend on the installation system and are not inferred from this sheet count. Product and assembly specifications also determine suitable thickness and layer requirements.
Assumptions & limitations
What this calculation assumes
- A rectangular room has uniform-height walls; selected layers apply to all covered surfaces.
What to keep in mind
- No panel layout, framing design, sloped ceilings, or fire-rated assembly selection.
Common questions
Can I estimate both sides of a partition?
Calculate each side as a separate surface. The layers field means repeated layers on the same covered area.
Why are openings restricted?
This room model requires some wall area to remain. For ceiling-only work, divide the ceiling area by sheet coverage separately.