Drywall Calculator

Estimate drywall sheets and cost for walls and ceilings with waste factor.

Wall Area (sq ft)
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Ceiling Area (sq ft)
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Total Area (sq ft)
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Wall Sheets Needed
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Ceiling Sheets Needed
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Total Sheets (incl. 10% waste)
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How the Drywall Calculator Works

This drywall calculator estimates the number of sheets needed for a room by computing the total paintable wall area. It multiplies the room perimeter (2 × length + width) by the ceiling height, then subtracts 21 sq ft per door and 15 sq ft per window. If you include the ceiling, it adds the floor area (length × width). The total area is divided by the sheet size — 32 sq ft for 4×8 sheets or 48 sq ft for 4×12 sheets — and a 10% waste factor is added to account for cuts and mistakes. Drywall is sold by the sheet, so always round up. For best results, plan separate orders for walls and ceiling, as ceiling drywall is often a different thickness (5/8 inch for fire resistance).

Frequently Asked Questions

How many sheets of drywall do I need for a 12×12 room?
A 12×12 room with 8-ft ceilings needs about 12–14 sheets of 4×8 drywall for walls and ceiling.
How much drywall do I need per square foot?
One 4×8 sheet covers 32 sq ft. Plan for 10% waste, so roughly 1 sheet per 29 sq ft of actual coverage.
Should I use 4×8 or 4×12 drywall sheets?
4×8 sheets are easier to handle and work for most rooms. 4×12 reduces seams on 9-ft walls.
How do I calculate drywall for a ceiling?
Multiply room length by width to get ceiling sq ft, then divide by sheet size (32 or 48) and add 10% waste.

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