Drywall Calculator
Estimate whole drywall panels from separate surfaces, openings, layer counts and actual sheet dimensions.
This tool runs entirely in your browser. Your data is never uploaded, never stored, and never leaves your device.
Pool separate wall/ceiling faces with openings and individual layer counts, then estimate whole panels from actual sheet dimensions.
How to use it
- 1Enter non-overlapping surface rectangles, measured opening deductions and layer counts.
- 2Enter one panel product's actual dimensions, your allowance and optional price per sheet.
- 3Review layer-adjusted coverage, whole panels and separate purchase-rounding surplus.
- 4Download the local JSON estimate; any edit clears the old result.
Example
- Input
- 26.4 m² layer-adjusted area, 10% allowance, 2.88 m² panels at USD 12.50 each.
- Output
- 29.04 m² required; 11 panels; 31.68 m² purchased; USD 137.50.
An area-based quantity example, not a cutting plan or installation specification.
What happens to your data
Room dimensions and prices are calculated locally without uploading or saving them. The optional JSON file contains active measurements and assumptions.
Last updated October 2026
A drywall sheet count starts with the surfaces actually being lined, not just the room's floor area. This calculator combines up to twenty wall or ceiling rectangles, subtracts openings from each face, applies that face's layer count and divides the pooled coverage by the actual panel dimensions. It then applies your chosen allowance and rounds once to whole sheets.
Keep one panel product in an estimate. The result separates layer-adjusted surface coverage, whole-sheet purchases and surplus caused by package rounding. You can add a price per panel for a materials-only subtotal and download the measurements and assumptions locally. It does not generate a cutting plan or select a fire-rated assembly.
How it works
For each rectangle, net face area = length × width − excluded opening area. Multiply this by the number of layers on that face, then add the separate rectangles. Required coverage = combined layer-adjusted area × (1 + allowance/100). Whole panels = ceiling(required coverage ÷ actual panel length ÷ actual panel width). Purchased coverage is whole panels × panel area; rounding surplus is purchased minus required coverage.
A wall lined on both sides has two distinct faces. Enter each face once, with its own openings and layer count. A two-layer face is different from a second face because its openings and product may differ. Ceilings can be additional rectangles. Break an L-shaped surface into non-overlapping rectangles rather than counting its bounding box, and keep sloped surfaces in their actual measured plane.
Deduct only openings you intend to exclude from coverage. The tool checks that a deduction does not exceed its rectangle, but cannot assess whether an opening's cutout can be reused or whether the chosen layout needs a full sheet across it. A zero-area rectangle contributes nothing; the combined net coverage must remain positive. Allowance is user-selected and begins at zero, rather than asserting one universal waste percentage.
Actual board length and width matter. Products can have different sheet sizes, thicknesses and edge profiles. Area division is a quantity estimate, not a promise that those sheets fit every stud bay or avoid butt joints. Cutting layout, orientation, support spacing and handling can increase purchases. USG's estimator likewise distinguishes coverage and product size from installation-dependent material use.
The optional cost multiplies whole sheets by your entered price per sheet. It excludes screws, nails, adhesive, joint tape, joint compound, trims, finishing, delivery, tax and labour. Currency is a label only. Decimal measurements use exact fractions at whole-sheet boundaries, but real coverage still depends on measured dimensions and the chosen installation. Any edit clears the old estimate and download.
Worked example: Two surfaces with different layer counts
- Input
- 5 × 2.4 m face, 2.4 m² excluded, 2 layers; 3 × 2.4 m face, no exclusion, 1 layer; 10% allowance; 2.4 × 1.2 m sheets; USD 12.50/sheet.
- Result
- 26.4 m² layer-adjusted coverage; 29.04 m² with allowance; 11 panels; 31.68 m² purchased; 2.64 m² rounding surplus; USD 137.50.
Example dimensions, allowance and price demonstrate quantity arithmetic, not a recommended assembly or market quote.
Common use cases
- Combine walls and ceilings with different opening areas before buying one panel product.
- Account for a second layer on selected surfaces without silently doubling the entire project.
- Compare actual sheet sizes and see the separate effect of allowance and whole-panel rounding.
- Keep a local JSON quantity record for a supplier conversation without uploading room measurements.
Frequently asked questions
How many drywall sheets do I need?＋
Combine each face's net area multiplied by its layer count, apply your chosen allowance, divide by the actual sheet area and round up once. The worked example needs 29.04 m² after allowance, so 2.88 m² sheets give 11 whole panels. Check layout and product instructions before ordering.
Should I subtract doors and windows?＋
Enter the measured opening area you intend to exclude, in the selected square units. A deduction does not prove you can reuse the cutout or reduce a whole sheet in the installation. Allow for your layout separately and avoid deducting the same opening twice on one face.
How are multiple layers and both wall faces handled?＋
Layers multiply the net area of that one entered face. Enter the opposite face as another rectangle, rather than assuming it has identical openings or specifications. All entries in a single estimate must use the same compatible panel product.
Does this estimate screws, compound or tape?＋
No. Those quantities depend on the board system, joints, fastener schedule and application. This tool estimates panel coverage and optional panel cost only. Use the actual manufacturer's installation and finishing guidance for other materials.
Does the allowance include cutting waste?＋
It includes only the percentage you enter. No cutting optimizer or universal waste percentage is imposed. You can see that allowance separately from the extra coverage caused by buying whole panels.
Are room measurements uploaded?＋
The estimate runs locally and does not upload or save entered measurements or prices. The optional JSON download includes active measurements and assumptions on your device. Editing an input removes the earlier result.
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