Enter your room size and pick the sheet you are buying - 4×8 or 4×12 - to get the drywall sheets, screws, joint compound and tape for the job. Sized for the boards Home Depot stocks.
Openings (deducted from walls)
Boarded area
45.6 sq ft
Screws
~64
Joint compound
~6 lb · 475 ft²/box
Joint tape
~17 ft
This is the standard drywall calculator set up for the sheet sizes Home Depot carries. It sizes both the boarding and the finishing from your room dimensions:
wall area = 2 × (length + width) × height
ceiling = length × width (if you board it)
sheets = ceil( (wall area + ceiling) × wastage ÷ sheet area )
screws = sheets × 32
compound = boarded area × 0.64 kg/m²
tape = boarded area × 1.2 m/m²
It treats the room as a closed box and lets the wastage allowance cover the offcuts around doors and windows - or add each opening to deduct it exactly. Boarding more than one room? Add a room for each and the sheets, screws, mud and tape total into one order. All math runs in exact metric internally, so switching units never changes the answer.
| Board | Size | Area | Use |
|---|---|---|---|
| 1/2 in standard | 4 × 8 ft | 32 sq ft | Walls and ceilings in most rooms |
| 1/2 in standard | 4 × 12 ft | 48 sq ft | Long walls - fewer joints to tape |
| 5/8 in Type X | 4 × 8 ft | 32 sq ft | Fire-rated walls, garages, ceilings |
| 1/2 in mold-resistant | 4 × 8 ft | 32 sq ft | Bathrooms and damp areas |
A 12 ft × 12 ft room, 8 ft ceilings, walls and ceiling boarded, 4 × 8 ft sheets, 10% wastage:
Work out the area to board - the walls (room perimeter × ceiling height) plus the ceiling if you are boarding it - then divide by the area of one sheet and add wastage. A 12 × 12 ft room with 8 ft ceilings and the ceiling boarded is about 528 sq ft; with 4 × 8 ft sheets (32 sq ft each) and 10% wastage that is 19 sheets. Enter your room above for the exact count.
Home Depot stocks standard 1/2 inch drywall in 4 × 8 ft sheets (32 sq ft) and 4 × 12 ft sheets (48 sq ft), plus 5/8 inch fire-rated board, 1/4 inch flexible board for curves, and moisture- and mold-resistant boards for bathrooms. The calculator defaults to 4 × 8 ft; switch to 4 × 12 ft if you are buying the longer sheets to cut down on joints.
Use 4 × 12 ft sheets where the wall is long enough to take them - fewer sheets means fewer butt joints to tape and sand, and a flatter wall. Stick with 4 × 8 ft sheets for small rooms, tight access, or if you are working alone, since the 12 ft boards are heavy and awkward to carry and lift. The calculator works out the count for whichever you pick.
Allow roughly 0.6 kg of joint compound per square metre of board for a taped, three-coat finish - about one 4.5 gallon (61.7 lb) box of all-purpose mud per 475 sq ft of board. For tape, allow about one 250 or 500 ft roll for a typical room. The calculator gives the compound and tape totals from your boarded area so you know how many boxes and rolls to grab.
About 32 coarse-thread drywall screws fix a 4 × 8 ft sheet to wood studs at 16 inch centres - a screw every 12 inches in the field and 8 inches around the edges. Ceilings are fixed more densely. A 1 lb box holds roughly 175-225 screws depending on length, so a small room is usually one box. The calculator multiplies your sheet count by 32.
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