How to measure for drywall
Measure each wall’s length and the floor-to-ceiling height in feet. The calculator multiplies the room’s perimeter by the height, deducts 21 sq ft per door and 15 sq ft per window, and adds the ceiling (length × width) when that option is on. Those opening allowances are standard estimating figures. Many hangers do not subtract small windows at all, because the cutout usually becomes scrap, so the 10% waste default already gives you a little cushion.
For a basement or garage where some walls stay unfinished, enter only the walls that get board, or work out the total area yourself and adjust the length and width to match.
Worked example: a 12 × 12 ft room with ceiling
These are the calculator’s defaults: 8 ft ceilings, one door, one window, 4 × 8 sheets, 10% waste and a pro install at the national average cost level.
| Item | Calculation | Result |
|---|---|---|
| Walls | 2 × (12 + 12) × 8 − 21 − 15 | 348 sq ft |
| Ceiling | 12 × 12 | 144 sq ft |
| Board area | 348 + 144 | 492 sq ft |
| Sheets | 492 × 1.10 ÷ 32 = 16.9, round up | 17 sheets |
| Screws | 17 × 32 sq ft × about 1 per sq ft | 544 screws |
| Joint tape | 492 × 370 ÷ 1,000 = 182 ft | 1 × 250 ft roll |
| Joint compound | 492 × 9 ÷ 1,000 = 4.4 gal | 1 × 4.5 gal pail |
| Hung, taped and finished | 492 × $1.50–$3.00 | $738 – $1,476 |
Doing it yourself, 17 sheets at a typical $14 each come to $238 before screws, tape, mud and tools. Note how close the compound figure is to a full pail: with heavier all-purpose compound, or walls with lots of outside corners, buy a second pail.
Choosing a sheet size
| Sheet | Sheets for 492 sq ft | Sheet cost at default prices | Approx. joint length |
|---|---|---|---|
| 4 × 8 ft | 17 | $238 | 185 ft |
| 4 × 10 ft | 14 | $224 | 172 ft |
| 4 × 12 ft | 12 | $216 | 164 ft |
Longer sheets mean fewer butt joints, where two untapered ends meet. Those seams are the hardest to finish flat because there is no recess for the tape and mud, so pros prefer 12 ft sheets for long walls and ceilings. The trade-off is weight and handling: a 1/2 in 4 × 12 sheet is a two-person lift and may not make it up a tight staircase. The 4 × 10 price in the calculator is interpolated halfway between typical 4 × 8 and 4 × 12 prices; enter your store’s price for an exact comparison.
Which board to use
Standard 1/2 in board covers most interior walls. Ceilings are often hung with 5/8 in board or 1/2 in sag-resistant ceiling board, especially with framing at 24 in on center. Use 5/8 in Type X where code requires a fire-rated assembly, such as a garage ceiling with living space above (the IRC calls for at least 1/2 in board on the garage side of walls shared with the house), and moisture- and mold-resistant board in bathrooms and basements. Behind tile in a shower, use cement board or a waterproofing system instead; the tile calculator covers the tile side of that job.
DIY or hire a pro?
Hanging board is approachable for a handy homeowner with a helper and, for ceilings, a rented drywall lift. Finishing is the hard part: taping, three coats of mud, and sanding to a smooth Level 4 finish takes practice, and every flaw shows once the wall is painted. A common compromise is to hang it yourself and hire a finisher. The pro estimate above covers hanging, taping and finishing per sq ft of board; the local cost level setting scales it for your area.
What’s not included
Demolition and disposal of old walls, framing repairs, insulation (see the insulation calculator), corner bead, texture, primer and paint (see the paint calculator), and tool or lift rental. Screws, tape and compound are listed as quantities but not priced.
How this calculator works
- Board area = 2 × (length + width) × height − doors × 21 − windows × 15 sq ft, plus length × width when the ceiling is included.
- Sheets = board area × (1 + waste %) ÷ sheet area, rounded up. Screws ≈ sheets × sheet area × 1 per sq ft.
- Tape rolls = board area × 370 ÷ 1,000 ÷ 250 ft, rounded up. Compound pails = board area × 9 ÷ 1,000 ÷ 4.5 gal, rounded up.
- Installed cost = board area × the national per-sq-ft range for hung, taped and finished drywall × local cost factor.
Assumptions and limitations
- Each door deducts 21 sq ft and each window 15 sq ft, standard estimating allowances.
- Sheet prices default to typical 2026 prices for 1/2 in board. The 4 × 10 price is interpolated halfway between the 4 × 8 and 4 × 12 prices because no published figure is in our dataset.
- Tape (370 ft) and ready-mix compound (9 gal) per 1,000 sq ft follow USG estimating figures; heavier all-purpose compound uses somewhat more. Screws at about 1 per sq ft is an editorial rule of thumb.
- The professional price covers hanging, taping and finishing per sq ft of board, multiplied by the local cost factor. Demolition, framing, insulation, texture and paint are not included.
- The DIY cost covers drywall sheets only; screws, tape, compound, corner bead and tools are listed as quantities but not priced.
These results are planning estimates, not quotes. Local prices, site conditions and building codes vary, so get written estimates from licensed contractors before you commit to a budget.
Frequently asked questions
- How many sheets of drywall do I need for a 12 × 12 room?
- With 8 ft walls, one door, one window and the ceiling, the board area is 492 sq ft. Add 10% waste and divide by 32 sq ft: 17 sheets of 4 × 8, or 12 sheets of 4 × 12.
- Should I use 1/2 in or 5/8 in drywall?
- Use 1/2 in for most interior walls. Use 5/8 in Type X where code requires a fire-rated assembly, such as a garage ceiling with living space above (the IRC requires at least 1/2 in board on the garage side of walls shared with the house), and often on ceilings with framing 24 in on center to reduce sag.
- Should I hang drywall horizontally or vertically?
- On walls up to about 9 ft, most pros hang sheets horizontally. It reduces the total length of seams and puts the tapered joint at a comfortable working height. Taller walls and commercial jobs are often hung vertically.
Sources and data
Prices are US national ranges reviewed October 2026. A few values are editorial estimates where no single published source exists; theCost Index marks each one. Read our methodology and editorial policy.