Estimating drywall looks simple: area divided by sheet size. But the waste comes from how sheets fit the walls, and the consumables are where many estimates fall short. A complete takeoff covers the board, the fasteners, the finishing materials and the beads, and treats ceilings, walls and wet areas separately.
Measure walls and ceilings
Measure the room perimeter and multiply by the wall height. Subtract large openings such as doors, windows and archways, but not small ones: you'll rarely use the offcut from a switch box or a small window. Add the ceiling area if you're boarding it. For sloped ceilings and gable walls, split them into rectangles and triangles.
Standard deductions: about 20 sq ft per door and 15 sq ft per typical window.
Pick the sheet size
In Canada, ½" drywall in 4×8 ft sheets is easiest to handle, with ⅝" Type X where fire separation is needed, such as between a house and an attached garage. 4×12 ft sheets mean fewer butt joints on long walls but need two people. Hanging sheets horizontally puts the hard-to-finish butt joints lower and fewer in number. On 9 ft walls, 54" wide sheets avoid a narrow strip at the top.
Choose the right board
- Standard board for most walls and ceilings.
- Moisture-resistant board in bathrooms and kitchens. Use a proper backer board behind tiles in showers.
- Fire-rated board where required, such as garage-to-house walls and ceilings.
- Acoustic board between bedrooms and on party walls.
- Thermal or insulated board on external walls.
List each board type as its own line, because they're priced differently.
Waste
10–12% covers most rooms. Go higher for rooms with lots of short walls, sloped ceilings, stairwells or many openings.
Consumables people forget
- Screws: roughly one per square foot of board. A 1 lb box covers about 300 sq ft.
- Joint compound: about one 17 L pail per 480 sq ft for three coats.
- Tape: about 370 ft per 1,000 sq ft of board.
- Corner bead for every outside corner and window reveal, plus stop bead at edges.
- Adhesive if you're gluing to studs.
- Sanding sheets or mesh, primer or mist coat for the decorator.
Finish levels
Drywall finish levels run from Level 0 (no taping) to Level 5 (a full skim coat). Level 4 suits most painted walls; Level 5 is for critical lighting and gloss finishes. Each level adds coats, compound and labour, so agree the level in writing before you price.
A worked example
A 14 × 12 ft room with 8 ft walls, one door and two windows: walls 416 sq ft − 50 = 366 sq ft, ceiling 168 sq ft, total 534 sq ft. With 12% waste that's 598 sq ft, or 19 sheets of 4×8. Two buckets of compound, a 500 ft roll of tape, 2 lb of screws, plus bead for any outside corners.
Labour
Hanging and finishing is often priced per sheet or per square foot. Ceilings, high walls and small rooms take longer per sheet, and stairwells often need scaffolding. Allow drying time between coats in your program: rushing it shows up as cracks and shrinkage.
The drywall calculator handles the whole room and the consumables in one pass, and the plaster calculator covers veneer plaster, base coats and stucco.
Checklist before you send the price
- Walls and ceilings measured separately, openings deducted
- Board types listed for wet, fire and acoustic areas
- Waste set for the room shapes
- Screws, finishing materials, tape and beads listed
- Finish level or skim agreed in writing
- Access equipment for ceilings and stairwells
- Waste removal and clean-up
Common questions
Should I hang ceilings or walls first?
Ceilings first. The wall boards then support the ceiling edges, and the joint is easier to finish.
How long before I can paint?
Joint compound needs to dry fully between coats, usually 24 hours per coat in normal conditions. Prime before painting.
Pricing per room vs per sheet
Pricing by area is fair to both sides on big, open jobs. On small rooms, bathrooms and stairwells, the setting-up, cutting and access time doesn't shrink with the area. Many contractors price small rooms as a fixed sum, or add a minimum charge.
This guide is general information for estimating. It is not engineering, legal or tax advice. Check local codes and your inspector for your project.