Estimating drywall looks simple: area divided by sheet size. But the waste comes from how sheets fit walls, and the consumables are where many estimates fall short.
Measure walls and ceilings
Measure the 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.
Standard deductions: about 20 sq ft per door and 15 sq ft per typical window.
Pick the sheet size
In the US, 4×8 ft sheets are easiest to handle. 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.
Waste
10–12% covers most rooms. Go higher for rooms with lots of short walls, sloped ceilings 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 4.5 gallon bucket 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.
- Adhesive if you're gluing to studs.
Labour
Hanging and finishing is often priced per sheet or per square foot. Remember that ceilings, high walls and small rooms take longer per sheet.
The drywall calculator handles the whole room and the consumables in one pass.
This guide is general information for estimating. It is not engineering, legal or tax advice. Check local codes and your inspector for your project.