Drywall Calculator

Estimate drywall sheets for a rectangular room, with separate wall and ceiling selection, openings, multiple layers, waste, material cost and an optional labor rate.

How to use the drywall calculator

Choose US customary or metric units.
Enter the inside dimensions of one rectangular room.
Select walls, ceiling or both. Subtract the combined area of doors and windows only from the selected surfaces.
Enter the number of board layers and the actual sheet dimensions available to you.
Set an allowance for cuts and breakage. Enter supplier prices and an optional labor rate in your own currency.

Drywall sheet formulas

Wall area = 2 × (room length + room width) × wall height

Ceiling area = room length × room width

Net surface area = selected wall and ceiling area − openings

Covered layer area = net surface area × number of layers

Sheets before waste = ceiling(covered layer area ÷ sheet area)

Sheets to buy = ceiling(sheets before waste × (1 + waste % ÷ 100))

The estimator rounds whole sheets upward before applying the allowance. Actual layout can require more or fewer sheets because offcuts, seams, orientation and room geometry are not modeled.

Worked drywall examples

1. Walls and ceiling in a 12 ft × 10 ft room

At 8 ft high, wall area is 352 ft² and ceiling area is 120 ft². Subtracting 40 ft² of openings leaves 432 ft². With 4 ft × 8 ft sheets, the result is 14 sheets before allowance and 16 sheets with 10% extra.

2. Walls only

For the same room, walls minus openings equal 312 ft². Dividing by 32 ft² per sheet gives 10 sheets before allowance and 11 sheets with 10% extra.

3. Metric room

A 4 m × 3 m × 2.4 m room has 33.6 m² of walls and a 12 m² ceiling. Subtracting 2 m² leaves 43.6 m². With 1.2 m × 2.4 m sheets, the result is 16 sheets before allowance and 18 sheets with 10% extra.

4. Two board layers

The first example has 432 ft² per layer. Two layers require 864 ft² of covered area. With 4 ft × 8 ft sheets, that is 27 sheets before allowance and 30 sheets with 10% extra.

5. Ceiling only

A 15 ft × 12 ft ceiling has 180 ft². With 4 ft × 12 ft sheets, the area method gives 4 sheets before allowance and 5 sheets with 10% extra. Layout may require additional boards.

6. Editable material and labor estimate

If an order requires 20 sheets at 16.50 each, sheet material is 330.00. If covered layer area is 600 ft² and the entered labor rate is 1.25 per ft², labor is 750.00 and the combined estimate is 1,080.00 in the entered currency.

Calculation limits

This calculator models one rectangular room and area coverage. Calculate irregular rooms as separate rectangles and avoid double-counting shared surfaces. Openings are subtracted once before multiplying by the number of layers. Confirm whether that matches your scope. Board type and thickness depend on location, assembly requirements and applicable codes; this calculator does not select them.

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Frequently asked questions

Does the calculator include the ceiling?

Only when Ceiling is selected. Walls and ceiling are controlled independently.

How are doors and windows handled?

Enter their combined area in the selected square unit. The value is subtracted once from the selected surface area.

Does it optimize the sheet layout?

No. It divides area by sheet area. Seams, orientation, staggered joints and offcut reuse require a layout plan.

Is 10% waste always correct?

No. It is an editable example. Room geometry, openings, board dimensions, handling and installer practices affect the allowance.

Can it estimate a double-layer assembly?

Yes. Set layers to 2. Confirm whether openings and labor pricing should be treated the same way for your project.

Does the cost include finishing materials?

No. Sheet cost and an optional area-based labor rate are included. Fasteners, tape, compound, corner bead, primer, delivery, tax and disposal are separate.

Planning the cavity fill too? Use the Insulation Calculator to estimate batts, rolls, boards or loose-fill packages after measuring the wall or ceiling area.