Drywall Calculator

Use this Drywall Calculator to estimate sheets for rectangular room walls, equal-length individual walls and an optional ceiling.

Estimated Result

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How to Use the Drywall Calculator

Choose whole-room mode and enter room length, width and height. For separate walls of equal length, choose wall-count mode: length is the length of each wall, and width is only the ceiling width. Enter total door and window areas once, choose a sheet size, then set waste and optional price. Results update as you edit; Reset restores the example.

Formula and Explanation

Wall area = 2 × (length + width) × height (room)
Or wall area = wall count × length per wall × height
Ceiling = length × width, when included
Net = walls + ceiling − doors − windows
Sheets = ceil(net × (1 + waste / 100) ÷ sheet area)

A 4 × 8 ft sheet covers 32 sq ft; 4 × 10 covers 40 and 4 × 12 covers 48. Waste is added once to net coverage before rounding sheets upward. The displayed waste area excludes the extra coverage created by whole-sheet rounding. Cost uses the rounded sheet count.

This is an area-based estimate, not a cutting or joint-layout optimization. Wall openings cannot exceed wall area. Multiple layers, angled surfaces, framing, fire ratings, fasteners, joint compound, labor and tax are not included. Measure unequal walls separately and combine their areas outside this equal-wall model.

Worked Example

A 12 × 10 ft room with 8 ft walls has 352 sq ft of walls. Including its 120 sq ft ceiling and deducting a 21 sq ft door plus a 15 sq ft window leaves 436 sq ft. With 10% waste, purchase coverage is 479.6 sq ft. Divide by 32 and round up to 15 sheets; at $15 per sheet the material estimate is $225.

Frequently Asked Questions

Does this optimize sheet cuts?

No. It divides allowance-adjusted area by sheet area. Seams, board orientation, framing and offcut reuse can increase the quantity you actually buy.

How are doors and windows deducted?

Enter the total measured door area and window area in square feet. They are subtracted once from wall coverage, including when a ceiling is selected.

What does wall-count mode mean?

All counted walls have the entered length and height. Width is used only for the optional rectangular ceiling. Use whole-room mode for the four walls of a rectangular room.

Does 10% waste include whole-sheet rounding?

The 10% is an editable planning allowance applied before rounding. Any surplus from purchasing whole sheets comes afterward and is not another percentage.