Plasterboard calculator: sheets, fixings and finish

How it works

Add each rectangular wall or ceiling, choose the locally sourced board, enter the total area of openings and set a cutting allowance. The sheet count uses net area divided by sheet area. It is an area-based estimate, not a board-by-board cut plan.

For simple rectangular surfaces, the calculator estimates screw lines from the entered framing spacing and the cited British Gypsum maximum fixing centres. It estimates joint tape from a full-sheet grid and skim plaster from the published 2 mm coverage.

Formula

• Estimate sheets

  Net area = wall and ceiling area − opening area Order area = net area × (1 + waste %) Sheets = ceil(order area ÷ selected sheet area)

  The result rounds the area-based sheet estimate up to whole boards.

• Estimate accessories

  Tape = full-sheet grid joint length Fixings = supported fixing runs × fixings per run at the cited maximum spacing Beads = ceil(measured external-corner length ÷ selected stock length)

  The accessory estimate assumes supported sheet edges and a simple rectangular layout. Opening edges and offcut reuse are not modeled.

• Estimate skim plaster

  25 kg bags = ceil(order area ÷ 10 m² per bag at 2 mm)

  The coverage is the Thistle MultiFinish manufacturer figure for a 2 mm finish.

Worked example

1. 1

   Enter one wall

   Wall = 3.6 m × 2.4 m = 8.64 m² Selected board = 1.2 m × 2.4 m = 2.88 m²

   This example has no openings and no cutting allowance.

2. 2

   Count boards and tape

   ceil(8.64 ÷ 2.88) = 3 sheets Two vertical joints × 2.4 m = 4.8 m of tape

   The simple grid uses three full-width boards with no offcut reuse.

3. 3

   Estimate fixings and finish

   81 wall screws 1 × 25 kg bags of Thistle MultiFinish at 2 mm

   The screw count uses 600 mm framing and 300 mm maximum wall fixing centres. One bag covers 10 m² at a 2 mm skim.

Assumptions and limits

The selected sheet and accessory data are specific manufacturer examples. Availability and system requirements vary. Confirm board suitability, framing, fixing schedule and finishing instructions for your project before ordering.

Openings reduce the board and finish area, but their position and perimeter are not modeled. The tape and fixing estimates therefore use the uncut rectangular surface grid and do not add fasteners around openings. Include extra cutting waste and check opening framing and jointing separately.

The British Gypsum guide gives different fixing centres for partitions, ceilings and external angles. This estimate applies the listed standard partition/ceiling figures only, system-specific requirements take priority.

Frequently asked questions