Drywall Calculator
The Drywall Calculator estimates the number of standard 4×8 ft (or 1.2×2.4 m) drywall/plasterboard sheets needed for a room, with the option to include the ceiling and a waste allowance for cuts. The waste factor is applied once to the combined total area (walls plus ceiling, if included) rather than per surface, so a project sitting just above a whole-sheet threshold before waste can round up by a full extra sheet from a small waste-percentage change. The metric sheet size (1.2 × 2.4 m = 2.88 m²) isn't a converted equivalent of the U.S. 4×8 ft sheet — a true conversion of 4×8 ft works out to about 2.97 m² — it's the actual standard plasterboard size sold in metric markets, so switching unit modes estimates for a genuinely different real-world product, not just a relabeled number. Like the Brick Calculator, this tool doesn't subtract door or window openings from the wall area, on the reasoning that offcuts around openings are usually reusable elsewhere on the same job.
Switch between U.S. Customary and Metric units.
How This Tool Works
Pick your units, then enter your room's length, width, and wall height. Optionally include the ceiling, and adjust the waste factor for your cutting needs.
Formula & Method
Wall area = room perimeter × wall height. If including the ceiling, add room length × width. Sheets needed = (total area × (1 + waste%)) ÷ sheet size — 32 sq ft per 4×8 sheet, or 2.88 m² per 1.2×2.4 m board.
Example Calculation
A 16×12 ft room with 8 ft walls, including the ceiling, at the default 10% waste: perimeter = 2 × (16 + 12) = 56 ft. Wall area = 56 × 8 = 448 sq ft. Ceiling area = 16 × 12 = 192 sq ft. Total area = 448 + 192 = 640 sq ft. With 10% waste: 640 × 1.10 = 704 sq ft. Sheets needed = 704 ÷ 32 = 22 sheets exactly. In metric, a 4×3.5 m room with 2.4 m walls, ceiling included: wall area = 2 × (4 + 3.5) × 2.4 = 36 m², plus a 14 m² ceiling = 50 m² total. With 10% waste: 55 m², which needs 55 ÷ 2.88 = 19.1, rounded up to 20 sheets of 1.2×2.4 m plasterboard.
Frequently Asked Questions
What size are standard drywall sheets?+
Most U.S. residential drywall sheets are 4×8 ft (32 sq ft); metric plasterboard is commonly 1.2×2.4 m (2.88 m²). Larger sheets are also available for bigger walls with fewer seams.
Can I calculate plasterboard in square meters?+
Yes — switch the unit toggle to Metric and enter your room in meters. The calculator sizes sheets as 1.2×2.4 m plasterboard.
Should I subtract doors and windows?+
For a quick estimate, skip small deductions since offcuts are often reused elsewhere. For precise ordering on a large job, measure openings and subtract their area.
Do I need different drywall for ceilings?+
Ceilings often use slightly thicker or sag-resistant drywall, especially over long spans — check your local building code and joist spacing.
Why does switching to metric change the sheet size, not just the units?+
Because 1.2 × 2.4 m (2.88 m²) is the actual standard plasterboard size sold in metric markets — it's not simply a unit conversion of the U.S. 4×8 ft (32 sq ft) sheet, which actually converts to about 2.97 m². Switching modes estimates for the real product sold in each market, so don't expect sheet counts to match exactly between a U.S. and metric run of the same room.
Does including the ceiling change the waste factor?+
No — the same waste percentage is applied to the combined wall-plus-ceiling area in a single step, not calculated separately per surface. If your ceiling has an unusual shape (vaulted, coffered) that needs more cuts than the walls, run it as its own calculation with a higher waste percentage instead.
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<a href="https://everyfix.net/tools/drywall-calculator/">Drywall Calculator</a> by <a href="https://everyfix.net">EveryFix</a>Related Tools
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