Plasterboard Calculator

How to Calculate Plasterboard for a Wall

Working out how many plasterboard sheets you need is straightforward once you know the method. Here is the step-by-step process professional plasterers use:

1. Measure the wall — record the total width and height in millimetres. For example, a standard UK room wall might be 3600mm wide and 2400mm tall.
2. Choose your sheet size — the most common UK plasterboard sheet is 2400 × 1200mm (8 × 4 feet). Smaller 1800 × 900mm sheets are easier to handle for DIY work.
3. Calculate how many sheets fit across — divide the wall width by the sheet width. For a 3600mm wall with 1200mm-wide sheets: 3600 ÷ 1200 = 3 columns.
4. Calculate how many rows — divide the wall height by the sheet height. For 2400mm with 2400mm sheets: 2400 ÷ 2400 = 1 row.
5. Multiply columns by rows — 3 × 1 = 3 sheets needed.
6. Account for openings — windows and doors reduce usable area but you still need to buy the full sheet. Our calculator accounts for this and shows you the true waste.

For the example above (3600 × 2400mm wall, standard sheets), you need exactly 3 plasterboard sheets with zero waste — a perfect fit.

UK Standard Plasterboard Sizes

The UK construction industry uses several standard plasterboard sheet sizes. The right choice depends on your project, ceiling height and how many people are available to lift the boards.

All sizes are available in 9.5mm, 12.5mm and 15mm thicknesses from UK suppliers like Wickes, B&Q and Screwfix.

Plasterboard Thickness Guide

Choosing the right plasterboard thickness is important for Building Regulations compliance, fire safety and sound insulation.

• 9.5mm — lightweight boards used for ceilings and dry-lining over smooth walls. Not suitable for stud walls on their own.
• 12.5mm — the standard thickness for walls. Provides adequate fire resistance (30 minutes) and sound insulation for most domestic applications. This is the default for UK new builds.
• 15mm — enhanced fire resistance and sound insulation. Required in some situations under UK Building Regulations Part B (fire safety) and Part E (sound). Common for party walls in flats and semi-detached houses.

For standard domestic walls, 12.5mm plasterboard is almost always the right choice. Check your building control requirements if you are working on party walls, fire compartments or commercial properties.

How to Reduce Plasterboard Waste

Plasterboard waste costs money and takes up skip space. Here are practical ways to minimise it:

• Try both orientations — our calculator automatically checks landscape and portrait layouts. Sometimes turning the sheets 90° eliminates edge cuts entirely.
• Reuse offcuts — a 400mm offcut from one sheet can fill a gap above a door. Plan your cutting order to maximise reuse.
• Use 3000mm sheets for tall walls — if your ceiling height is 2700mm, a 3000mm sheet covers it in one piece instead of needing a filler strip.
• Match sheet width to stud spacing — UK studs are typically at 400mm or 600mm centres. A 1200mm sheet spans exactly two or three stud bays.
• Order the right amount — over-ordering "just in case" leads to leftover sheets that often get damaged in storage. Use our calculator for an accurate count.

Dot and Dab vs Screw Fixing

There are two main methods for fixing plasterboard to walls in the UK:

Dot and Dab (Adhesive Fixing) — used when fixing directly onto block or brick walls. Blobs of plasterboard adhesive (such as Gyproc Dri-Wall or Thistle Bond-It) are applied to the wall in a grid pattern. The board is pressed into place and levelled. This method is faster and doesn't require a timber frame.

Screw Fixing (Mechanical) — used when fixing to timber studs or metal channels. Drywall screws (typically 32mm for 12.5mm board) are driven through the board into the frame at 300mm centres around edges and 400mm centres in the field. This is the standard method for stud walls, ceilings and metal-frame partitions.

Our calculator estimates both adhesive bags and screw counts so you can order the right fixings for your method.

Frequently Asked Questions

How many plasterboard sheets do I need for a room?

Measure each wall separately and add the totals together. A typical 4m × 3m room with 2.4m ceilings has two 4000mm walls and two 3000mm walls. Calculate each wall individually using our calculator, accounting for windows and doors, then sum the sheet counts.

What is the standard plasterboard size in the UK?

The standard UK plasterboard sheet is 2400 × 1200mm (approximately 8 × 4 feet) with a 12.5mm thickness. This size is stocked by all UK builders merchants and fits standard 2.4m ceiling heights.

Should I fit plasterboard horizontally or vertically?

It depends on your wall dimensions. Fitting vertically (portrait) is standard for walls up to 2400mm high with standard sheets. Fitting horizontally (landscape) can reduce the number of joints on shorter walls. Our calculator tries both orientations and recommends the one that uses fewer sheets.

Do I need to board over windows and doors?

No — you cut the plasterboard around openings. However, you still need to buy full sheets and cut them on site. The offcut waste from openings is unavoidable, but larger offcuts can sometimes be reused elsewhere.

How much plasterboard adhesive do I need?

For dot-and-dab fixing, you need approximately 0.5 bags (12.5kg) of plasterboard adhesive per standard 2400 × 1200mm sheet. A 25kg bag covers roughly two sheets. Our calculator estimates the total bags needed based on your sheet count.

What thickness plasterboard should I use?

For standard domestic walls, use 12.5mm plasterboard. Use 9.5mm for ceilings and dry-lining, or 15mm where enhanced fire resistance or sound insulation is required (check UK Building Regulations Part B and Part E).

How do I calculate plasterboard waste?

Waste comes from two sources: edge cuts (where sheets don't divide evenly into the wall) and opening cuts (around windows and doors). Our calculator works out the exact waste for your wall dimensions and shows it visually in the cutting diagram.