Plywood Thickness Explained: A Guide for DIY and Construction

Plywood is one of the most versatile materials used in joinery, construction and DIY. Whether you’re building shelving, a cabinet, or flooring, the success of your project often comes down to one key choice: plywood thickness.

Selecting the right thickness impacts strength, durability, weight, and even the overall look of your finished piece. In this guide, we’ll explain how to choose the right ply thicknesses UK buyers will commonly find, explore standard sizes, and give you practical recommendations for typical applications.

Understanding Plywood Thickness

Nominal vs Actual Thickness

When buying plywood, you’ll notice it’s listed in sizes such as 12mm or ¾ inch plywood. These numbers represent the nominal thickness. However, the actual measurement can be slightly reduced because of the sanding during the manufacturing stage, for example, 12mm plywood might measure closer to 11.5mm.

This small difference is crucial to note for projects where precision is important, for example, cabinet making or shelving. Always check both the nominal and actual thickness before you buy.

Ply Count and Core Materials

The number of layers (plies) and the type of core also affect strength. More plies usually mean greater stability, while hardwood cores offer extra durability compared to softwood or composite cores.

This is why 9mm plywood with a hardwood core might outperform a lower-quality 12mm sheet. When choosing thickness, it’s worth considering both the ply count and the core material alongside the measurement itself.

Common Plywood Thicknesses and Their Uses

Different projects require different levels of strength and rigidity. Here are some of the most widely used options.

Plywood Thickness Guide
Thickness	Typical Uses
2mm plywood	Very thin and lightweight; used for crafts, models, and decorative panels.
3.6mm plywood	Lightweight panelling, drawer bottoms, or cabinet backs.
5.5mm plywood	Wardrobe backs, interior panelling and drawer bases.
9mm plywood	Furniture carcasses, partition walls; more stability than thinner sheets.
12mm plywood	General construction, shelving, wall panelling; versatile all-rounder.
15mm plywood	Stronger option for shelving carrying moderate to heavy loads.
18mm / ¾ inch plywood	Heavy-duty; ideal for flooring, staircases and large furniture projects.

These are the most standard plywood dimensions available in the UK. For more specific applications, view our
full plywood product range.

Key Factors to Consider the Right Plywood Thickness:

1. Project Type

Identifying the specific needs of your project is the first step in selecting the right plywood thickness. A bookshelf needs thicker panels for the shelves than for the backboard. A wardrobe might use 18mm plywood for the sides, but 5.5mm for the rear. Always think about which parts of your project will bear weight. It’s a good idea to consult design plans and guidelines to ensure the plywood thickness aligns with the overall design and functionality of your project.

2. Load-Bearing Capacity

Consider both the weight and the distance between supports. For example, long unsupported spans of shelving should use 15mm plywood or thicker to prevent sagging.

3. Finish and Appearance

Thicker plywood is usually more stable and offers a smoother surface if you’re applying laminates, veneers or paint. For visible surfaces, investing in a slightly thicker sheet can improve the final finish.

4. Plywood Grades

Plywood is also graded (A, B, C, etc.), which affects appearance and quality. Higher grades have fewer imperfections and are better for visible finishes, while lower grades are more suited to structural or hidden applications.

FAQs: Plywood Thickness Explained

1. What is the thinnest plywood available?

The thinnest sheets are usually 2 mm to 3.6 mm plywood. They’re not structural, but useful for panelling, craft or furniture backing.

2. How thick is 5.5 mm plywood and what is it used for?

5.5 mm plywood is usually around half a centimetre thick. It’s commonly used for drawer bottoms, wardrobe backs and cabinet linings.

3. What’s the best plywood thickness for shelves?

For decorative shelves or light storage, 12 mm plywood works well. For bookshelves or heavy-duty shelving, use 15 mm plywood or 18 mm (¾ inch) to avoid sagging.

4. Can I use 1/2 inch plywood for a subfloor?

Yes, 12 mm plywood (around ½ inch) can be used for subfloors in some cases, but in the UK, 18 mm plywood is more typical for flooring because it provides greater strength and stability.

5. Does plywood thickness affect appearance?

Yes. Thicker panels are more stable and provide a smoother surface for finishing. If appearance matters, a thicker board can deliver a more professional result.

Tailored Plywood Solutions from Alexander Cleghorn

At Alexander Cleghorn, we supply a wide range of plywood thicknesses alongside other sheet materials, all available cut-to-size. Our in-house services – including CNC machining, edge banding and panel cutting, mean every board is prepared to your exact requirements, ready for use in furniture, interiors, shop fitting or construction.

If you’d like advice on the best material for your project, or want to order precision-cut panels, get in touch with our team today.

If you’d like to chat about your next project, fill out our form below.

Comprehensive Guide to Choosing the Right Plywood Thickness for Your Project

Understanding Plywood Thickness

Nominal vs Actual Thickness

Ply Count and Core Materials

Common Plywood Thicknesses and Their Uses

Key Factors to Consider the Right Plywood Thickness:

1. Project Type

2. Load-Bearing Capacity

3. Finish and Appearance

4. Plywood Grades

FAQs: Plywood Thickness Explained

Tailored Plywood Solutions from Alexander Cleghorn