Drywall Calculator

To calculate drywall sheets, find the total square footage of the surfaces you're covering (wall area = perimeter x ceiling height; ceiling area = length x width), subtract the area of doors and windows, then divide by the square footage of your chosen sheet size. Add a waste factor of 10-15% for cuts and mistakes. Our calculator handles all of this automatically - just enter your room dimensions.

The most common drywall sheet is 4 feet wide by 8 feet long (32 sq ft). For rooms with higher ceilings, 4×12 sheets (48 sq ft) are popular because they reduce seams. 4×9, 4×10, and even 4×16 sheets exist but are less commonly stocked at hardware stores.

A 10% waste factor is the industry standard for straightforward rectangular rooms. Bump it to 15% for rooms with angled ceilings, lots of corners, archways, or complex shapes. If you're a first-timer doing a DIY project, 15-20% gives you a safer buffer - running short mid-project means a second trip to the store, which nobody wants.

Yes - doors and windows are openings with no drywall, so they should be subtracted from your total wall area. Our calculator subtracts a standard door (3x7 ft = 21 sq ft) and a standard window (3x4 ft = 12 sq ft) per opening. For unusually large doors or custom windows, adjust manually by using fewer openings or tweaking your waste factor accordingly.

1/2-inch drywall is the most common choice for interior walls and ceilings in residential construction. It's lighter and easier to handle. 5/8-inch drywall is thicker, provides better soundproofing and fire resistance, and is required by code in many commercial applications and garage-to-home walls. Both come in the same sheet dimensions - this calculator works for either thickness.

Yes. Double-layer drywall (applying two sheets on top of each other) doubles your material requirement. It's used for soundproofing, fire-rated walls, or added structural rigidity. Our calculator includes a double-layer option that automatically multiplies your sheet count by two.

For a 12×12 room with 9-foot ceilings (walls only): perimeter = (12+12) × 2 = 48 linear feet; wall area = 48 × 9 = 432 sq ft. Subtract 1 door (21 sq ft) and 1 window (12 sq ft) = 399 sq ft net. With 10% waste, that's about 439 sq ft, or 14 standard 4×8 sheets. Add the ceiling (144 sq ft) and you're looking at roughly 18–19 sheets total.

Ceiling drywall is simply length × width of the room. For a 15×20 ft room, the ceiling is 300 sq ft. Divide by 32 (for 4×8 sheets) and you get about 9.4, so 10 sheets. Add your waste factor on top. Ceiling work is notoriously harder to cut precisely, so 15% waste is a smart buffer for ceilings specifically.

Absolutely. You can add up to 10 rooms in this calculator, making it useful for multi-room commercial spaces like offices, retail, and hospitality. For large commercial projects, remember that sheet count is just part of the picture - you'll also need joint tape, drywall screws, corner beads, and joint compound. Budget roughly 1 lb of drywall screws per 500 sq ft and one roll of tape per 300 sq ft.

At 1,000 sq ft of wall/ceiling area, you need about 32 sheets of 4×8 drywall (31.25, rounded up) or about 21 sheets of 4×12 drywall (20.8, rounded up), before waste. With a 10% waste buffer, plan for 35 sheets of 4×8 or 23 sheets of 4×12.

Beyond the sheets, a typical drywall job needs: joint compound (also called "mud") - roughly 1 gallon per 100 sq ft; paper or fiberglass mesh joint tape - about 1 roll per 300 sq ft; drywall screws - 1 lb per 500 sq ft for 1/2-inch drywall; corner bead for all outside corners; and primer before painting. Professional finishers also use a pole sander and multiple mud coats for a smooth finish.

Horizontally is generally preferred for walls in residential construction - it reduces the total number of seams, puts the long seam at a comfortable taping height, and can bridge studs more efficiently. Vertical installation is common in commercial work and with 54-inch or taller sheets. For ceilings, drywall always runs perpendicular to the joists regardless of orientation.