Quick answer: 2440 × 1220mm — roughly 8ft × 4ft — is the main full-sheet plywood size you will see across our range. The right thickness depends on what you are making, but thickness is only part of the decision. A 12mm marine plywood, 12mm birch plywood and 12mm general-purpose hardwood plywood are three different products with different specifications and intended uses.
If you already know which plywood type you need, choose the thickness on that product rather than looking for a separate 6mm, 9mm, 12mm or 18mm plywood page. We group thicknesses as variants so you can compare the correct material in one place.
What is the standard plywood sheet size?
For most of the plywood we stock, the full sheet is 2440 × 1220mm. This is commonly called an 8 × 4 sheet.
That does not mean every plywood sheet made in the UK market is 2440 × 1220mm. Specialist boards can come in other formats. Always check the actual product dimensions before planning a cutting list.
Browse the current range on our Plywood Sheets collection.
Which plywood thicknesses do Wern-Wood stock?
| Plywood type | Current thicknesses | Best reason to choose it |
|---|---|---|
| Structural Hardwood WBP Plywood | 3.6, 5.5, 9, 12, 15, 18 and 25mm | Construction work where the declared plywood specification suits the job. Our current board is EN 314-2 Bonding Class 2 and EN 636. The thin 3.6mm and 5.5mm options should not be assumed suitable for structural use simply because they sit within the same product range. |
| General Purpose Hardwood Plywood | 12 and 18mm | Dry internal joinery, shelving, boxing and general utility work where a structural specification is not required. |
| Birch Plywood | 4, 6, 9, 12 and 18mm | Furniture, cabinetry, joinery and projects where a smoother finish and stable sheet are important. |
| BS 1088 Marine Plywood | 6, 9, 12 and 18mm | Projects that specifically justify a marine plywood specification or face demanding moisture-prone conditions. |
| Shuttering Plywood | 12 and 18mm | Formwork, boarding, hoarding and general site work where utility matters more than a furniture-grade finish. |
| Anti-Slip Phenolic Birch Plywood | 12 and 18mm | Hard-wearing floors and platforms where an anti-slip film-faced surface is useful. |
Does thicker plywood mean better plywood?
No. Thickness tells you how thick the panel is. It does not tell you the bond class, veneer quality, structural declaration, surface finish or whether the plywood is suitable for moisture exposure.
For example, 18mm general-purpose hardwood plywood may be thicker than 12mm marine plywood, but that does not make it a better choice for a job that specifically requires BS 1088 marine plywood.
Choose the plywood type and specification first, then choose the thickness required for the project.
What are 4mm and 6mm plywood normally useful for?
Thin plywood is useful where low weight and flexibility matter more than stiffness. Typical examples include liners, templates, backing panels, curved work and lightweight joinery, depending on the actual plywood type.
Our 4mm birch and 6mm birch options are aimed at joinery and furniture-type work. Our 6mm marine plywood gives a thinner option where the marine specification is required.
What are 9mm and 12mm plywood normally useful for?
9mm and 12mm boards sit in a useful middle ground. Depending on the plywood type, they can be used for supported panels, joinery, cabinets, boxing, linings and other general sheet work.
The application still decides the product. If the job needs marine plywood, buy the marine board. If it is dry internal joinery, general-purpose hardwood or birch may be the more sensible choice.
What is 18mm plywood normally useful for?
18mm is popular because it gives a noticeably stiffer sheet and more fixing depth than thinner panels. It is commonly chosen for cabinetry, shelving, heavier panels, platforms and construction work where the product specification and support arrangement are suitable.
Do not use “18mm” as a substitute for checking the grade. We stock several completely different 18mm plywood products because the job matters as much as the thickness.
What about 25mm plywood?
Our structural hardwood plywood range includes a 25mm option for jobs that need a substantially thicker panel. That does not automatically make it suitable for a particular span or load. Structural work should follow the project specification rather than a generic thickness rule.
Can Wern-Wood cut plywood to size?
Yes. On eligible sheet products you can select the cutting option and enter your measurements before adding the product to your basket.
You still buy the full sheet. We cut the sheet you purchase to your measurements; we do not sell only the cut pieces and charge by square metre.
This is useful when an 8 × 4 sheet will not fit in your vehicle, when you want cleaner repeat cuts, or when the project needs panels that are easier to handle.
How should you choose plywood thickness?
- Start with the job. Is it furniture, dry internal joinery, construction, formwork, marine work or an anti-slip floor?
- Choose the correct plywood type and specification. Do not use thickness to compensate for the wrong grade.
- Check the support and loading. Floors, roofs, platforms and structural work need the thickness and fixing arrangement required by the project.
- Then choose the nearest suitable thickness in that product range.
If you are still deciding between the different plywood types, start with our full plywood range.
