Drywall Calculator

How many sheets of drywall do I need?

This drywall calculator divides the area you are covering by 32 square feet, the face of one standard 4 × 8 ft sheet, and rounds up to whole sheets. The formula is sheets = (length × height) ÷ 32. One 16 ft wall at 8 ft tall is 128 sq ft, which is exactly 4 sheets.

Enter the total length of wall in the Length field and the wall height in the Width field. For a whole room, add the ceiling area to the total. Then enter your sheet price and tick the waste box.

The formula in plain words

1. Area: add up every wall as length × height, plus the ceiling as length × width.
2. Sheets: area ÷ 32.
3. With waste: sheets × 1.10.
4. Round up to a whole sheet, then multiply by the sheet price.

The calculator is set for 4 × 8 sheets. Longer sheets cover more, so if you use 12 ft board, divide the area by 48 yourself.

Worked examples

1. One wall: 16 ft long, 8 ft high, $13 per sheet

• Area: 16 × 8 = 128 sq ft
• Sheets: 128 ÷ 32 = 4 sheets, costing $52.00
• With 10% waste: 4.4, rounded up to 5 sheets, costing $65.00

2. Bedroom: 12 × 14 ft, 8 ft ceiling, walls and ceiling

• Walls: (12 + 14) × 2 = 52 ft of wall × 8 ft = 416 sq ft
• Ceiling: 12 × 14 = 168 sq ft
• Total: 416 + 168 = 584 sq ft (enter 584 × 1)
• Sheets: 584 ÷ 32 = 18.25, rounded up to 19 sheets, costing $247.00
• With 10% waste: 20.1, rounded up to 21 sheets, costing $273.00

Drywall sheet sizes and coverage

Sheet size	Square feet	Sheets per 1,000 sq ft	Where it helps
4 × 8 ft	32	31.3	Standard, easy to carry
4 × 9 ft	36	27.8	9 ft walls hung vertically
4 × 10 ft	40	25.0	10 ft walls, fewer butt joints
4 × 12 ft	48	20.8	Long walls and ceilings, fewest seams
54 in × 12 ft	54	18.5	9 ft walls hung horizontally in two rows

Thickness	Common use
1/4 in	Curved walls, overlaying old plaster
3/8 in	Repairs, double-layer assemblies
1/2 in	Standard interior walls; sag-resistant versions for ceilings
5/8 in Type X	Fire-rated assemblies, garages, ceilings on wider framing

Moisture and special areas

Bathrooms, laundry rooms, and basements are usually hung with moisture-resistant board. Inside a tub or shower surround that will be tiled, many tile setters use cement backer board instead, which the backer board calculator sizes in 3 × 5 ft sheets. Run those areas through the calculator separately, so you do not order standard board for them.

How to measure a room for drywall

• Walk the perimeter. Add the lengths of every wall in feet. On an 8 ft ceiling, multiply by 8.
• Add the ceiling. Room length × width.
• Gables and slopes: a triangular gable wall is half its base × its height.
• Closets count. Measure inside closets, soffits, and the returns around window openings.
• Plan sheet layout for big walls. Hanging 12 ft sheets horizontally on a 12 ft wall leaves one long seam per row instead of several butt joints, which saves finishing time.

Common drywall mistakes

• Counting floor area instead of wall area. A 12 × 14 room is 168 sq ft of floor but 416 sq ft of walls.
• Forgetting the ceiling board type. Standard 1/2-inch board can sag on ceilings. Use a ceiling-rated or 5/8-inch board.
• Not buying finishing supplies. Each sheet needs mud, tape, and screws. Use the drywall mud calculator for joint compound.
• Ordering too few sheets of the long size. Long sheets often have to be special ordered. Count them separately from 4 × 8s.

Before the board goes up, check framing and insulation with the stud calculator and the insulation calculator. Afterward, the primer calculator covers the first coat on new board. To price the taping and finishing, see the drywall finishing cost calculator.