Drywall Calculator

1. Enter room dimensions. Measure the room length, width, and ceiling height in feet. The calculator includes the ceiling in its total, since hanging ceiling drywall is part of most room finishing projects. If you are doing walls only, subtract the ceiling area from the result.
2. Enter door and window counts. Standard interior doors are 3 ft × 7 ft (21 sq ft). Standard windows are approximately 3 ft × 4 ft (12 sq ft). The calculator deducts these from the gross area. If your doors or windows are significantly larger than standard, adjust the count accordingly or subtract the extra area manually.
3. Read the sheet count. The result shows sheets of standard 4 ft × 8 ft drywall (32 sq ft each) with a 10% waste factor already applied. This waste accounts for cuts around doors, windows, outlets, and the inevitable damaged sheets. Do not skip the waste factor on your actual order.
4. Note the finishing supplies. The calculator also estimates joint compound buckets (4.5 gallon) and tape rolls (500 ft). These are approximate. Most pros use 3 coats of compound, so having extra on hand is recommended.

Example: a 14 ft × 12 ft room with 8 ft ceilings, 1 door, and 2 windows has a gross area of 488 sq ft (416 sq ft walls + 168 sq ft ceiling). After deducting 45 sq ft for openings, the net area is 443 sq ft. With 10% waste, you need 487 sq ft covered, or 16 sheets of 4×8 drywall.

Drywall is sold and installed by the sheet. Standard 4×8 sheets cover 32 sq ft. The 10% waste factor accounts for cuts, broken corners, and fitting around electrical boxes and outlets.

4×12 sheets (48 sq ft each) are available and reduce seams on 8 ft walls, but are heavier and harder to handle alone. On 9 ft or 10 ft ceilings, use 54-inch-wide sheets or hang drywall horizontally to minimize butt joints. Butt joints (factory-cut ends meeting end-to-end) are harder to finish invisibly than tapered edges, so plan sheet layout to minimize them at eye level.