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Interior walls & ceilings

Drywall Calculator

Estimate complete gypsum-board sheets from measured room surfaces, exact panel dimensions, and a visible project allowance.

  • Walls plus optional ceiling
  • Metric & imperial
  • No hidden waste

Room walls & ceiling

Enter the room and panel

Measurement system
Panel size

This device

Saved estimates

Save an estimate to keep it here. Data stays in this browser.

Transparent by design

Drywall sheet formula

The engine calculates the perimeter wall area of one rectangular room, adds the ceiling only when selected, subtracts your measured openings, and divides by the exact panel area.

Wall areaAwalls = 2 × (length + width) × heightNet areaAnet = walls + ceiling − openingsOrder areaAorder = Anet × (1 + waste ÷ 100)Complete sheetsSheets = ceil(Aorder ÷ panel area)

The result is deliberately an area estimate, not a cut plan. Longer boards can reduce joints in some layouts, while obstructions, multiple layers, board orientation, damaged edges, and fire-rated details can increase the real order.

Worked example

A 12 ft × 12 ft room with ceiling

Use 8 ft walls, 24 ft² of measured openings, 4 × 8 ft panels, and a 10% allowance.

  1. 01
    Walls2 × (12 + 12) × 8 = 384 ft²
  2. 02
    Add ceiling, subtract openings384 + 144 − 24 = 504 ft²
  3. 03
    Add 10% allowance504 × 1.10 = 554.4 ft²
  4. 04
    Round complete sheetsceil(554.4 ÷ 32) = 18 sheets
Verified result18 complete 4 × 8 ft sheets

Confirm a workable panel layout, board type, required layers, and supplier dimensions before buying.

Common questions

Drywall calculator FAQ

Separate measured quantity from layout and assembly decisions.

How many drywall sheets do I need?

Measure the rectangular room length, width, and wall height; choose whether to include the ceiling; subtract the combined measured opening area; and enter the exact sheet size. BuildMeasure divides the allowance-adjusted area by the sheet area and rounds only the final purchase quantity upward.

Does this calculator include doors and windows?

Yes, when you enter their combined measured area. The calculator does not assume a standard door or window size because actual openings vary.

What drywall sheet sizes can I use?

Convenience presets cover 4 × 8, 4 × 10, and 4 × 12 ft sheets. Custom mode accepts the exact width and length printed by your supplier, including physical metric dimensions.

Is the waste allowance automatic?

No hidden allowance is applied. The field is visible and adjustable from 0% to 50%; choose a value based on layout, cuts, handling, breakage, and your installer or supplier guidance.

Does the result include joint compound, tape, screws, or framing?

No. This version estimates whole gypsum-board sheets only. It does not invent accessory quantities or prescribe a fastening schedule, board type, fire rating, moisture rating, or wall assembly.

Can the estimate replace a drywall layout?

No. It is area-based and does not optimize seams, offcuts, orientation, framing alignment, multiple layers, or code requirements. Verify a workable layout before ordering.

Continue planning

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