Drywall Calculator
Estimate the sheets of drywall (plasterboard) for a room’s walls and ceiling.
Last reviewed 2026-06-06
Hanging drywall starts with one number: how many sheets. Order short and the job stalls; over-order and full sheets are awkward to store and return. This calculator sizes both walls and ceiling.
Enter the room dimensions, choose whether to include the ceiling, and pick your sheet size. We total the surface area, add a standard waste allowance, and return the number of sheets.
How to use the Drywall Calculator
- Measure the room length, width and wall height.
- Choose whether to include the ceiling.
- Pick the sheet size you’ll buy (4×8 is easiest to handle; 4×12 means fewer joints).
- Read the number of sheets, which already includes 10% waste.
Frequently asked questions
How many sheets of drywall do I need?
Add the wall area (room perimeter × height) to the ceiling area if you are boarding it, add about 10% for waste, and divide by the area of one sheet (32 sq ft for 4×8, 48 sq ft for 4×12). This calculator does it for you.
Should I subtract doors and windows?
For a quick estimate, no. Counting whole walls and keeping a 10% waste allowance covers small openings and leaves you useful offcuts. For a large opening like a patio door, you can reduce the wall length slightly.
What size drywall sheet should I use?
4×8 ft sheets are the easiest to carry and fit through doorways. 4×12 ft sheets cover more area with fewer seams (less taping), which is great for ceilings and long walls but heavier and harder to manoeuvre.
How much extra drywall should I buy?
Around 10% is standard to cover cuts, breakage and offcuts that are too small to use. Tight, simple rooms can use a little less; rooms with many corners or openings, a little more.