How many sheets of drywall do I need for a room?

Measure the total length of the walls you're boarding and multiply by the ceiling height to get the gross wall area, subtract the combined area of doors and windows, then divide by the area of one panel, add a waste allowance (10% is standard), and round up to the next whole sheet. This calculator does all of those steps for you and adds a material cost estimate.

What is the standard size of a drywall sheet?

4 x 8 ft (roughly 1200 x 2400mm) is the most common size in the US and Canada. Most of Europe, the UK, and Australia stock metric boards in similar or slightly taller formats — 1200 x 2400mm, 1200 x 2600mm, or 1200 x 2700/3000mm — with the taller sizes chosen to board a full wall height with fewer horizontal joints.

Do I need special drywall for a bathroom or ceiling?

Yes, in most cases. Bathrooms, kitchens, and other damp areas call for a moisture- or mould-resistant board rather than standard board, and ceilings generally need a thicker board (or closer support spacing) than walls to resist long-term sagging. Garages, boiler rooms, and some shared or escape-route walls may also require a fire-rated board under local building regulations — check what applies to your specific room before you buy.

What plasterboard size is available in Gibraltar?

Gibraltar's building suppliers primarily stock imported UK-format plasterboard in the standard 2400 x 1200mm size, with taller 2700mm and 3000mm boards also available to order for full-height walls — confirm current stock and lead times with your local builders' merchant before ordering.

Plasterboard Calculator — How Many Sheets Do I Need?

How Many Sheets of Drywall Do I Need? Drywall Calculator Guide

Drywall is sold by the whole sheet, not by the square metre or square foot, so the real question before a wall or ceiling job isn't "how much area am I covering" — it's "how many sheets do I need to buy." This calculator converts your wall (and optional ceiling) area, minus door and window openings, straight into a panel count and material cost, so you order the right quantity in one trip instead of guessing and making a second run to the merchant.

The part a quick mental estimate usually gets wrong is everything that isn't a plain rectangle. Door and window openings subtract real area you don't need to board, a sloped gable wall adds a triangular section a simple length-times-height sum misses, and every job loses some sheet to offcuts a bare area-divided-by-panel-area formula ignores. This tool accounts for all of it — openings, slopes, and a waste allowance — and rounds the result up to the next whole panel, so the number you see is the number you can actually order.

How to use the drywall calculator

Enter the total wall length and wall height for the area you're boarding — the calculator multiplies these into a gross wall area.
Toggle "include ceiling" on if you're also boarding the ceiling, then enter the ceiling length and width to add that area in.
If any wall is a gable or sloped section, enter the base and height of the triangular cutout so that extra area is added correctly rather than left out.
Enter how many doors and windows are in the area, along with their height and width, so their combined area is subtracted from the gross total.
Choose a panel size preset (commonly 1200 x 2400mm, or 4 x 8ft in the US/Canada) or enter a custom size, then set your waste percentage — 10% is a sensible default.
Enter the price per panel to get an instant material cost alongside your panel count.

The drywall calculation formula, explained

The core formula is: net area = gross wall area (plus ceiling area and any sloped-wall triangle, if included) minus the combined area of all doors and windows. Panels needed = ceil[ (net area / single-panel area) x (1 + waste percent) ] — you divide the area you actually have to cover by how much one panel covers, inflate that by your waste allowance, then round up, since a supplier will not sell you a fraction of a sheet.

The waste allowance exists because real jobs are never a perfect grid of full sheets — corners, stud lines, and small offcuts too short to reuse all eat into your coverage, so building that loss into the formula up front avoids running short mid-job.

Worked example: a room with 14m of total wall length and a 2.4m ceiling height gives a gross wall area of 14 x 2.4 = 33.6 m².
One door at 2.03m x 0.86m = 1.746 m², and one window at 1.2m x 1.0m = 1.2 m², for combined openings of 2.946 m².
Net area = 33.6 - 2.946 = 30.65 m² (rounded).
Panel size: 1200 x 2400mm (1.2m x 2.4m) = 2.88 m² per panel. Raw panel count = 30.65 / 2.88 = 10.64 panels.
Add 10% waste: 10.64 x 1.10 = 11.71 panels.
Round up to the next whole panel: 12 panels to buy.

Pro tips and common mistakes

Standard sheet sizes are not the same everywhere, and mixing them up is the single most common ordering mistake: 4 x 8 ft (roughly 1200 x 2400mm) is the North American standard, while continental Europe, the UK, and Australia mostly stock 1200 x 2400mm, 1200 x 2600mm, or 1200 x 2700/3000mm metric boards depending on wall height. Always confirm the exact size your local supplier stocks before you finalise a panel count.

Worked example at Gibraltar prices: a room with 14m of total wall length and a 2.4m ceiling, minus one door and one window, comes to a net area of roughly 30.65 m². At 2.88 m² per standard 2400 x 1200mm sheet with 10% waste, that's about 12 sheets. At a typical price of around £15 per sheet for imported UK-format stock, budget approximately £180 in plasterboard alone before screws, jointing compound and a tradesperson's labour.

Gibraltar's builders' merchants mostly stock imported UK-format board (2400/2700/3000 x 1200mm), so sheet sizes, terminology ("plasterboard" rather than "drywall"), and British Gypsum/Gyproc branding follow UK convention rather than a separate local standard.

Match thickness to the job: 9.5-12.5mm boards are standard for most interior walls, while thicker 15-16mm boards suit ceilings (sag resistance matters more overhead) and fire-rated partition walls.
Use a fire-rated board ("Type X" or the local equivalent) around garages, boiler rooms, and shared walls where regulations require extra fire resistance — standard board is not a substitute.
Use a moisture- or mould-resistant board (often green- or blue-faced) in bathrooms, kitchens, and utility rooms — standard board can absorb moisture and break down behind tile or paint.
Ceilings need a thicker or more closely-supported board than walls to resist long-term sagging — check the span table for your joist or furring-channel spacing rather than assume a wall board works overhead.
Buy a couple of panels beyond your calculated waste allowance if the room has many corners, alcoves, or a complex ceiling shape — the standard 10% default assumes a fairly simple rectangular layout.