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Walls & decorating

Drywall calculator

Estimate wall and ceiling sheets, openings, layers and whole-sheet costs. See clear formulas, worked examples, assumptions and a printable estimate.

Drywall & Plasterboard Calculator

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Walls, ceilings & openings

Optional deductions reduce the estimate. Opening positions and usable offcuts are not calculated.

Each row is ONE face. Enter both sides of a partition separately, or use Identical surfaces only when dimensions, openings and layers match. All rows use the same sheet product.

Sheet size

Editing a dimension selects Custom. Switching units converts the same physical sheet; it does not change the selected format.

Estimate method & allowance

Separate: round each surface and each layer up, without sharing sheets between them. Combined: pool all board area, then round once, assuming offcuts can be shared. Both are area estimates, not cutting layouts.

The starting 10% is an editable example. Sheet orientation, seams, framing and offcut shape may require more material than either estimate.

Sheet cost

Starting price is an example; replace it with your supplier’s price. Currency changes the label only. Screws, tape, compound, framing, labor, tax and delivery are excluded.

How to useCalculation methodRead the project guide

How to use

  1. Add walls and ceilings separately. Enter the dimensions, identical-surface quantity and number of layers for each.
  2. If you choose to subtract openings, add them to their own surface. Openings are repeated for every identical copy of that surface.
  3. Choose a sheet preset or custom actual sheet dimensions. Set an allowance and the price per sheet.
  4. Compare Separate surfaces with Combined area. The combined figure assumes sharing material and is only an area estimate.

Calculation method

For each surface, subtract its openings from width × height, then multiply by identical-surface quantity and layers. Separate surfaces rounds each face’s allowance-adjusted area up to whole sheets before multiplying by layers and quantity. Combined area sums the layer areas, applies the allowance and rounds once. Cost equals purchased sheets × price per sheet.

Worked example

One 4 × 2.4 m wall has 9.6 m². With one layer, 10% allowance and 1.2 × 2.4 m sheets (2.88 m² each), the estimate is 4 sheets, or 60 USD at 15 USD each. Subtracting a 0.9 × 2 m opening leaves 7.8 m² and produces 3 sheets. Two separate 1 m² faces with no allowance need 2 sheets in Separate surfaces or 1 sheet in Combined area.

Assumptions and limits

The tool does not optimize sheet placement, joints or offcuts. It does not choose board type, fire rating, moisture resistance, fixings, framing or code compliance. Subtracting a doorway can reduce area without removing the cutting work. Labor, joint compound, tape, screws, delivery and tax are excluded.

Units, prices and saved estimates

Physical values are stored internally in metres, square metres, cubic metres or kilograms as appropriate. Changing measurement units converts their display; choosing a currency changes its label without applying an exchange rate. Purchase quantities use unrounded calculations. Money is shown to two decimal places.

Edits can be saved in this tab. Optional device saving lasts seven days after the last save. Copy, TXT download and a separate printable report use the current valid estimate. Delete draft removes saved inputs without resetting the visible form. The privacy choices page can remove all calculator drafts.

For practical measurement decisions, read planning drywall sheets, layers and openings.