Drywall Calculator

The formula

Coverage and yield assumptions

Sheet sizes are nominal: 4 × 8 ft = 32 sq ft, 4 × 10 = 40 sq ft, 4 × 12 = 48 sq ft. Screw count assumes about one screw per square foot of board, which matches typical spacing of 12 in on ceilings and 16 in on walls with framing at 16 in on center as described in the USG Gypsum Construction Handbook. A 1-5/8 in coarse-thread screw is standard for 1/2 in board on wood studs.

Choosing sheet size and thickness

Longer panels mean fewer butt joints and less taping. A 12 ft sheet can span a whole wall in many bedrooms, but it weighs around 80 lb at 1/2 in and needs two people and a straight path into the house. Use 4 × 8 sheets where stairways, hallways or a solo installer make big boards impractical.

Half-inch is the common wall thickness. Ceilings often use 1/2 in sag-resistant or 5/8 in board, and 5/8 in Type X is required in places such as attached garage walls shared with living space under many codes. Bathrooms and laundry rooms usually get moisture-resistant panels; tile surrounds in showers need cement board instead.

Hanging order and layout

Hang the ceiling first so wall sheets support its edges. On walls, run sheets horizontally when the room is 8 or 9 ft tall: two rows cover the height with one horizontal seam at a comfortable taping height. Stagger butt joints between rows and avoid joints that line up with the corners of doors and windows, where cracks tend to start.

Finishing materials

Plan on paper or mesh tape for every seam, all-purpose or lightweight joint compound, corner bead for outside corners, and a setting-type compound for the first coat if you want fast, hard fills. A typical finish takes three coats of compound plus sanding. The Gypsum Association's GA-214 describes finish levels 0–5; most painted walls are finished to Level 4, and Level 5 adds a skim coat for glossy paint or harsh side lighting.

Delivery tips

• Ask for the boards to be stocked inside, room by room, to save your back.
• Store sheets flat, off a damp slab, and keep them dry.
• Order a few extra sheets on big jobs; returning one is easier than a second delivery.

Common mistakes to avoid

• Forgetting closets, soffits and the ceiling of a stairwell.
• Ordering 4 × 12 sheets that cannot turn the corner of a narrow stair.
• Placing seams directly at the corners of doors and windows, where cracks form.
• Overdriving screws through the face paper, which weakens the hold.
• Using regular board in a shower instead of cement board.

Waste factor

10% is a sensible default for rooms with a few doors and windows. Use 5% for big plain walls where full sheets fit cleanly and 15% for rooms with many angles, soffits, stair walls or cathedral ceilings, where offcuts pile up quickly.

Imperial and metric

Switch the toggle above the inputs to enter ft ↔ m. The page converts metric entries to imperial before calculating, using NIST factors (1 ft = 0.3048 m, 1 in = 2.54 cm), and shows key results in both systems.

Worked examples

Bedroom with ceiling

Inputs: room length 14 ft; room width 12 ft; wall height 8 ft; include ceiling?: Yes, walls and ceiling; sheet size: 4 × 8 ft (32 sq ft); waste factor 10%.

Result: You need 21 drywall sheets.

• Units to buy (rounded up): 21 sheets
• Wall area: 416 sq ft (38.6 m²)
• Ceiling area: 168 sq ft (15.6 m²)
• Total board area: 584 sq ft (54.3 m²)
• Screws (about 1 per sq ft): 672

Basement walls only, 4 × 12 sheets

Inputs: room length 24 ft; room width 18 ft; wall height 8 ft; include ceiling?: No, walls only; sheet size: 4 × 12 ft (48 sq ft); waste factor 10%; cost per unit $19.5.

Result: You need 16 drywall sheets.

• Units to buy (rounded up): 16 sheets
• Wall area: 672 sq ft (62.4 m²)
• Ceiling area: 0 sq ft (0 m²)
• Total board area: 672 sq ft (62.4 m²)
• Screws (about 1 per sq ft): 768
• Estimated material cost: $312.00

Tall great room

Inputs: room length 20 ft; room width 16 ft; wall height 10 ft; include ceiling?: Yes, walls and ceiling; sheet size: 4 × 12 ft (48 sq ft); waste factor 15%.

Result: You need 25 drywall sheets.

• Units to buy (rounded up): 25 sheets
• Wall area: 720 sq ft (66.9 m²)
• Ceiling area: 320 sq ft (29.7 m²)
• Total board area: 1,040 sq ft (96.6 m²)
• Screws (about 1 per sq ft): 1,200

Quick reference for common sizes

The table repeats the first worked example at smaller and larger sizes, keeping every other setting the same, so you can see how the drywall calculator result scales.

Limitations

The estimate covers flat rectangular rooms. Gable walls, soffits, closets and stairwells must be measured and added separately. Screw counts vary with framing spacing and fastening schedule, so follow the board maker's instructions and local code.