How to Calculate Materials for a Plasterboard Job
Without Running Short or Wasting Money

Getting your plasterboard order wrong costs you in two ways - a second merchant run or paying to skip waste. Here is a straightforward method that experienced drylining contractors use on every job, whether it is a single partition wall or a full house first fix.

What You Need Before You Start

Before you can calculate anything, gather these measurements:

• Total wall and ceiling area in m2 (length x height for each surface)
• Deductions for doors and windows (opening width x height)
• Stud centres (typically 400mm or 600mm)
• Board size you intend to use (most common: 2400 x 1200mm or 2700 x 1200mm)
• Number of layers (single or double for fire or acoustic ratings)

Step 1 - Calculate Your Net Area

Add up the area of every surface being boarded. Then subtract openings:

For example: a room with 42m2 of wall area, two doors (each 2.1 x 0.9m = 1.89m2) and one window (1.2 x 1.0m = 1.2m2) gives a net area of 42 - 3.78 - 1.2 = 37.02m2.

Step 2 - Add a Waste Allowance

Plasterboard cannot be ordered to the nearest board without running short. You will always have cuts, especially around openings and at ceiling junctions. A standard waste allowance is 10% for straightforward rooms and up to 15% for heavily detailed rooms with lots of cuts.

On our example: 37.02 x 1.10 = 40.72m2.

Step 3 - Convert to Board Count

Divide your wastage-adjusted area by the area of one board:

• 2400 x 1200mm board = 2.88m2 per board
• 2700 x 1200mm board = 3.24m2 per board

Using 2400 x 1200mm boards: 40.72 / 2.88 = 14.1 boards - order 15.

Always round up to the next whole board. Never round down.

Step 4 - Calculate Screws

Screw spacing depends on stud centres. As a rule of thumb:

• At 400mm stud centres: approximately 32 screws per board
• At 600mm stud centres: approximately 24 screws per board

Plasterboard screws typically come in boxes of 200 or 1000. For 15 boards at 400mm centres: 15 x 32 = 480 screws - so 3 boxes of 200.

Step 5 - Jointing Compound and Tape

These quantities are often under-estimated. General guidance:

• Jointing compound: allow 1kg per linear metre of joint (3 coats combined)
• Paper tape: total linear metres of all board joints - usually around 70-80% of the board count in metres
• Corner bead: measure all external corners

Common Mistakes to Avoid

• Forgetting ceilings - a common one. Always add ceiling area separately before calculating.
• Not accounting for board orientation - boards should generally be fixed with the long edge perpendicular to the studs to minimise joints.
• Under-ordering compound - a skim finish requires significantly more compound than a tape and joint finish.
• Mixing board thicknesses - standard partition walls use 12.5mm; fire-rated partitions may need 15mm. Double-check your spec.

Ordering Tips

Always confirm with your merchant whether boards are sold individually or in packs - some suppliers sell in packs of 6 or 8. If you need 15 boards and packs come in 8, you will need 2 packs (16 boards). The extra board is cheap insurance.

Also check delivery lead times. Plasterboard is bulky and some merchants require 24-48 hours notice for full packs. Ordering on the day you need it is a common cause of delays.