Drywall Calculator
Estimate drywall sheets, joint compound, and tape for a room or whole project. Enter wall and ceiling dimensions and your sheet size to get sheet count plus the mud and tape to finish it. Includes a waste factor for cuts and offcuts.
Drywall Sheet Layout
How the Formula Works
Calculate total wall area
Total Area = Wall Height × Wall Width × Number of Walls Multiply all three inputs — subtract door/window openings manually if needed
Calculate net sheets required
Sheets (net) = ⌈Total Area ÷ Sheet Area⌉ Sheet area: 4×8 = 32 ft², 4×10 = 40 ft², 4×12 = 48 ft²
Apply waste factor
Sheets (order) = ⌈Net Sheets × 1.10⌉ 10% waste accounts for cuts at corners, outlets, and windows
Estimate joint compound
Compound (gal) = Total Area × 0.011 Covers standard Level 4 finish (tape coat plus two finish coats). Quantities vary by finish method.
Estimate tape
Tape (lf) = Total Area × 0.5 One linear foot of tape per two square feet of drywall — approximates seam density
Frequently Asked Questions
Multiply each wall's height by its width to get the area, then add all walls together. Divide the total area by the sheet size (32 ft² for a 4×8 sheet, 40 ft² for 4×10, 48 ft² for 4×12) and round up. Add 10% for waste: Sheets = ⌈Total Area ÷ 32⌉ × 1.10. For a room with four 9×12 ft walls, that's 4 × 108 = 432 ft² ÷ 32 = 13.5 → 14 sheets × 1.10 = 16 sheets to order.
4×8 ft sheets are the most common and easiest to handle — one person can carry them. 4×12 ft sheets reduce horizontal seams on 9-foot ceilings (one sheet covers the full height, no butt joint in the middle) which saves finishing time. 4×10 ft is a compromise. Use 4×12 on tall walls if you have help handling them; use 4×8 for repairs, closets, or solo work.
Plan for about 0.011 gallons of joint compound per square foot of drywall for a standard Level 4 finish. For a 432 sq ft room, that's about 4.8 gallons (roughly one 5-gallon bucket). Buy all-purpose compound for the tape coat and topping or lightweight compound for finish coats — or use all-purpose for all coats on smaller jobs.
A good rule of thumb is one linear foot of tape per two square feet of drywall. For a 432 sq ft room, that's about 216 linear feet of tape. Paper tape is preferred by professionals for strength; fiberglass mesh tape is easier for beginners. Buy tape in 75–500 ft rolls — for most rooms, two 150-ft rolls is enough.
Add 10% for typical rectangular rooms with standard door and window placements. Increase to 15% for rooms with many angles, arched openings, or complex ceilings. The waste comes from cut pieces at corners that can't be reused, outlet and switch cutouts, and the occasional cracked sheet. This calculator adds 10% automatically.
A standard 12×12 room with 9-foot ceilings has four walls: 2 walls at 12×9 ft = 216 ft² and 2 walls at 12×9 ft = 216 ft², total 432 ft². At 32 ft² per 4×8 sheet: 432 ÷ 32 = 13.5, round up to 14 sheets, plus 10% waste = 16 sheets. The ceiling adds another 144 ft² = 5 sheets (net) = 6 with waste — so roughly 22 sheets total for walls and ceiling.
½-inch (12.7 mm) drywall is standard for interior walls and ceilings in residential construction — it fits standard framing at 16 or 24 inches on center. ⅝-inch (15.9 mm) is used for fire-rated assemblies, garages, and commercial projects. ¼-inch is for curved walls or laminating over existing drywall. ⅜-inch is rarely used today. Use ½-inch for most projects unless code requires otherwise.
A standard 4×8 sheet of ½-inch drywall costs $12–$20 depending on brand and region. Specialty types (moisture-resistant, fire-rated) cost more. For a 16-sheet order at $15 per sheet, material cost is $240. Add joint compound ($20–$40 for a 5-gallon bucket), tape ($5–$15), screws ($10–$20), and corner bead ($20–$40). Professional installation adds $1.50–$3.50 per sq ft for labor on top of materials.