Drywall Calculator
A room with 200 linear feet of wall at 8 feet high needs about 53 sheets of 4x8 drywall after subtracting doors and adding 10% for waste. Enter your total wall length, ceiling height, and the number of openings to get an accurate drywall sheet count. The calculator subtracts door and window areas, adds your chosen waste factor, and tells you exactly how many full sheets to buy.
Quick answer
Total wall area is the perimeter (linear feet) multiplied by the ceiling height.
What this tells you
- •Total wall area is the perimeter (linear feet) multiplied by the ceiling height.
- •Each standard door or window opening subtracts square footage from the total.
- •A waste factor (typically 10%) accounts for cuts, mistakes, and unusable pieces.
- •The form models 4-foot-wide sheets with the selected 8- or 12-foot length.
- •Sheet count does not choose thickness, fire rating, moisture resistance, fasteners, or finish level.
How to Use
- 1Measure the total linear feet of wall to be covered (add up all wall lengths).
- 2Enter the wall height in feet (standard is 8 feet).
- 3Count the number of door and window openings.
- 4Set the average opening size (21 sq ft for a standard interior door).
- 5Click Calculate to see how many sheets you need.
How It Works
Formula
Wall Area = Length(ft) x Height(ft)
Net Area = Wall Area - (Openings x Opening Size)
Sheets = ceil(Net Area x (1 + Waste%) / Sheet Size)The calculator multiplies your total linear wall footage by the ceiling height to get gross wall area. It subtracts the combined area of all openings, then multiplies by the waste factor and divides by the area of one sheet. The result is rounded up because you always buy whole sheets.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Standard bedroom with 3 doors
Small bathroom with no windows
Drywall Sheets by Room Size (10% Waste, 4x8 Sheets)
Approximate sheets needed for common room sizes with no openings subtracted. Subtract about 1 sheet per standard door or window.
| Room Size | Perimeter | 8 ft Ceiling | 9 ft Ceiling |
|---|---|---|---|
| 10 x 10 ft | 40 ft | 11 sheets | 13 sheets |
| 10 x 12 ft | 44 ft | 13 sheets | 14 sheets |
| 12 x 12 ft | 48 ft | 14 sheets | 15 sheets |
| 12 x 14 ft | 52 ft | 15 sheets | 17 sheets |
| 14 x 16 ft | 60 ft | 17 sheets | 19 sheets |
These counts include 10% waste but do not subtract openings. For each standard door (21 sq ft), subtract roughly 1 sheet from the total.
How to Estimate Drywall for a Room
Step 1: Measure the perimeter. Add up the length of every wall that needs drywall. For a rectangular room, this is 2 x (length + width). A 12 x 14 ft room has a 52-foot perimeter.
Step 2: Subtract openings. A standard interior door is about 21 sq ft (3 x 7 ft). A typical window is about 12 sq ft (3 x 4 ft). Multiply the count of each by its area, and subtract that from the gross wall area. Skipping this step leads to over-ordering.
Step 3: Add waste. Plan for 10% waste on straightforward rooms. Bump it to 15% for rooms with lots of corners, soffits, or angled walls. Waste covers cuts around outlets, seams that do not line up, and damaged pieces.
Openings need care. The form multiplies one average opening area by the count, so a mix of doors and windows should be measured separately or converted to a weighted average. Small openings do not always save a proportional amount of board because the surrounding sheet may still be needed for layout and stronger joints. Subtracting too aggressively can undercount material.
Area alone does not create a hanging plan. Stud spacing, wall height, sheet orientation, butt-joint placement, inside and outside corners, backing, stair walls, soffits, arches, and access determine how pieces can be cut. Sketch each wall and place seams before ordering when material handling or finish quality matters.
Longer sheets can reduce joints but require more space, helpers, and lifting capacity. A 12-foot board may not turn through a stairwell or doorway. Ceiling boards and thicker or rated panels can be heavy and awkward. Plan delivery, storage, lifts, and safe handling rather than choosing the fewest sheets from area alone.
Drywall type belongs to the assembly design. Thickness, core type, mold and moisture resistance, impact resistance, tile-backer requirements, and exterior or shaft products are not interchangeable. Wet areas may require cementitious or approved tile substrates rather than ordinary gypsum board. Product instructions and the approved assembly control.
Fire-resistance and sound ratings apply to complete tested assemblies, including framing, layers, fastener type and spacing, joint treatment, insulation, penetrations, and sealants. Buying a panel labeled Type X does not by itself create a rated wall. Do not use this count to alter a garage separation, corridor, shaft, multifamily separation, or other regulated assembly.
Finishing materials are outside the calculation. Tape, joint compound, corner bead, screws, adhesive, sealant, texture, primer, and accessories depend on sheet layout and finish level. Level 5 work uses more labor and compound than a utility area. Fastener length and spacing depend on panel thickness, framing, layers, orientation, and applicable instructions.
The implementation sets net area to zero if entered openings exceed gross wall area, then can return zero sheets. That protects the arithmetic from a negative area but does not validate the measurements. Recheck the wall schedule whenever openings approach or exceed the gross area.
Common mistakes
- Forgetting to include the ceiling when it also needs drywall (this calculator covers walls only).
- Underestimating waste on rooms with many corners, closets, or angled walls.
- Not subtracting door and window openings, which leads to buying too many sheets.
- Using 4x12 sheet counts when the store only stocks 4x8 sheets, or the other way around.
- Subtracting every opening by area without checking whether the sheet layout actually saves a board.
- Adding wall lengths that do not all share the entered height.
- Assuming sheet count also includes ceiling board, screws, tape, compound, bead, or primer.
- Using a panel name as proof that the complete wall meets a fire, moisture, or sound requirement.
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