Home & Construction⏱ 5 min read
How to Calculate Plasterboard Quantities for Any Room
Plasterboard (drywall) calculations require knowing board size, the layout that minimises cuts, and how to account for doors, windows, and ceiling changes. Here is the complete method.
Ordering the right amount of plasterboard saves money and avoids the cost of a second delivery. The calculation is straightforward once you know the board dimensions and how to handle openings.
Standard Board Sizes
Board SizeAreaCommon Use
2400mm x 1200mm2.88 m2Standard walls and ceilings
2700mm x 1200mm3.24 m2Higher ceilings
3000mm x 1200mm3.60 m2Commercial / high ceilings
1200mm x 900mm1.08 m2Small areas, patching
Step-by-Step Wall Calculation
Step 1: Calculate gross wall area
(treat each wall as a full rectangle)
Room: 4.5m x 3.8m, 2.4m ceiling
Wall 1: 4.5 x 2.4 = 10.80 m2
Wall 2: 4.5 x 2.4 = 10.80 m2
Wall 3: 3.8 x 2.4 = 9.12 m2
Wall 4: 3.8 x 2.4 = 9.12 m2
Total gross: 39.84 m2
Step 2: Deduct openings
Door (0.9 x 2.1m): 1.89 m2
Window (1.2 x 1.0m): 1.20 m2
Total deductions: 3.09 m2
Step 3: Net area
39.84 - 3.09 = 30.75 m2
Step 4: Add 10% waste
30.75 x 1.10 = 33.83 m2
Step 5: Boards needed (2400x1200 = 2.88 m2 each)
33.83 / 2.88 = 11.75 → order 12 boards
Ceiling Calculation
Ceiling area = Room length x Room width
4.5 x 3.8 = 17.1 m2
Add 10% waste:
17.1 x 1.10 = 18.81 m2
Boards needed: 18.81 / 2.88 = 6.53 → order 7 boards
Total for room (walls + ceiling): 12 + 7 = 19 boards
Thickness and Type Guide
TypeThicknessUse
Standard (ivory)9.5mm or 12.5mmGeneral walls and ceilings
Moisture resistant (green)12.5mmBathrooms, kitchens
Fire resistant (pink)12.5mm or 15mmGarages, between floors
Acoustic (soundboard)12.5mm or 15mmParty walls, home cinema
Insulated (backed with PIR)30-100mm totalExternal walls, drylining
Screws and Jointing Compound
Plasterboard screws: approximately 15-18 screws per board
For 19 boards: 19 x 17 = 323 screws → buy 350 (one box of 500)
Jointing tape: 1 roll (90m) covers approximately 15-20 boards
For 19 boards: 1-2 rolls
Jointing compound (for scrim tape method):
Approximately 1kg per board for a 3-coat finish
For 19 boards: 19kg → buy 20kg (two 10kg buckets)