Drywall Calculator

How this calculator works

The calculator turns the surface you're covering into sheets, then derives the finishing materials — screws, joint compound, tape, and corner bead — from the same area using industry rules of thumb. The core math:

wall area = 2 × (length + width) × height     (room mode)
area      = walls + ceiling − deductions (if enabled)
sheets    = area × (1 + waste %) ÷ sheet sq ft → rounded up
screws    = sheets × 32 (per 4×8 sheet at 16" studs)
compound  = area ÷ 450 sq ft per 4.5-gal bucket → rounded up
tape      = area × 0.37 lf ÷ 250 ft rolls → rounded up

If you already know your square footage — a whole basement, several rooms, a garage — switch to direct area mode and enter wall and ceiling areas straight in. Every rule of thumb above (screws per sheet, compound coverage, tape per square foot) is an editable assumption under advanced options, and each one is listed with your results.

One deliberate choice worth knowing: by default the calculator does not subtract doors and windows. Estimators generally ignore openings smaller than about 32 sq ft because the cutout piece is rarely reusable elsewhere — you still buy the sheet. A checkbox turns deductions on if your walls are mostly glass.

Worked example: a 12 × 12 ft room with ceiling

Take a 12 × 12 ft room with 8 ft walls, doing the ceiling too, with 4×8 sheets and 10% waste:

• Walls: 2 × (12 + 12) × 8 = 384 sq ft.
• Ceiling: 12 × 12 = 144 sq ft. Total: 528 sq ft.
• Sheets: 528 × 1.10 = 580.8 sq ft; ÷ 32 sq ft per 4×8 sheet = 18.15 → 19 sheets.
• Screws: 19 sheets × 32 = 608 screws → one 1,000-count box.
• Compound: 528 ÷ 450 = 1.17 → two 4.5-gal buckets of ready-mix.
• Tape: 528 × 0.37 = 195 linear ft of joints → one 250 ft roll.

Those are the default inputs above — run it and you'll see the same numbers, each with its calculated (unrounded) value beside the purchase quantity.

How to measure for drywall

• Walls:measure the room's length and width at the floor and the wall height floor-to-ceiling. The calculator multiplies the perimeter by the height. For a single wall or an odd space, use direct-area mode instead.
• Ceilings:length × width covers flat ceilings. For vaulted ceilings, measure the actual sloped surface (it's longer than the floor below it) and add it in direct-area mode.
• Count outside corners — the corners that point into the room, like a boxed-out chimney or a wall return. Each needs a full-height corner bead. Inside corners just get tape.
• Note your stud spacing (16 or 24 inches on center) — it affects how many screws each sheet takes and which sheet thickness is appropriate.

See How to Measure a Home Project for measuring technique and tools.

Buying drywall and finishing materials

• Pick sheet length to minimize joints. A 12 ft wall hung horizontally with 4×12 sheets has one long seam and no butt joints; the same wall in 4×8s adds two butt joints per course — the hardest joints to finish flat.
• Standard thickness is 1/2 inch for walls. Ceilings on 24-in centers typically want 5/8-in board (it resists sagging and is required in some garage and fire-separation locations). Moisture-resistant board belongs in baths and laundry rooms — but not inside tiled showers, which need cement board.
• Ready-mix all-purpose compound is the simplest choice for DIY taping and finishing. Setting-type powder compounds cure faster and harder but are less forgiving to sand.
• Take delivery on bigger jobs. Sheets are heavy, fragile at the corners, and awkward in anything smaller than a full-size truck. Most yards deliver cheaply, and some will carry sheets into the room.
• Buy coarse-thread screws for wood studs (fine-thread for steel), 1-1/4 in for 1/2-in board on wood.

Common estimating mistakes

• Deducting every door and window.The scrap from a window cutout usually isn't usable elsewhere, so deducting openings under-orders sheets. That's why the deduction toggle defaults to off.
• Skipping the layout sketch. The area math says 18.15 sheets; the real count depends on how sheets land on your walls. Ten minutes with graph paper before ordering beats a second trip.
• Underestimating finishing materials. Mud and tape are cheap compared to sheets, but running out mid-coat costs a day. Round up — unopened buckets keep.
• Forgetting the ceiling adds fast. A 12 × 12 ceiling is 144 sq ft — nearly five more 4×8 sheets, plus a helper or a rented lift to hang them.
• Ignoring waste on complicated rooms.Closets, soffits, angles, and stairwells chew up sheets. Use 15% waste instead of 10% when the room isn't a simple box.

Limitations

This tool estimates quantities from area; it does not produce a hanging layout, so the true sheet count for a specific room can differ by a sheet or two depending on orientation and where joints land. It assumes one uniform sheet size, standard 250 ft tape rolls and 8 ft corner bead, and does not itemize primer, sanding supplies, adhesive, resilient channel, insulation, or vapor barriers. Fire-rated, moisture-resistant, and abuse-resistant assemblies have code-driven material requirements this calculator does not check — confirm those with your local building department.