Sheet sizes and thicknesses, in millimetres and in inches

Before working out how many sheets to buy, you need to know how big the sheet is, and it is not the same everywhere: it changes with the material, the manufacturer and the country. Here are the most common sizes and thicknesses in millimetres, the ones used in the United States and Canada in inches, and why “3/4” plywood is not 3/4.

The most common sizes, in millimetres

In Europe, and in most of the world, sheets are sold in millimetres. The most widespread size is 2440 × 1220 mm, above all in plywood and MDF. In melamine and chipboard each manufacturer has its own, and they tend to be larger.

These are the most common, not the only ones: there are thinner and thicker boards, and other sizes. The ones for the sheet you are going to buy are on its label or on the supplier’s website.

Length, width and grain

In Europe, sizes are given length first. On a sheet with grain, real wood or melamine that imitates it, the grain almost always runs along the length: on a 2800 × 2070, along the 2800. The optimizer sees it the same way: a part that follows the grain is placed with its length along the length of the sheet.

In the United States it is the other way round, width first: 4 × 8 feet, 48 × 96 inches. Whichever way round you get the sizes, check which way the grain runs before cutting.

Thickness: the one on the label and the real one

Thickness matters in the cut list: parts that fit between others are two thicknesses shorter, as in the cut list for a cabinet. If the sheet does not measure what its label says, neither will the furniture.

A 19 mm board may be a few tenths of a millimetre over or under, and in a piece of furniture you won’t notice. With American plywood the difference is bigger: it is sold by its nominal size, and “3/4” plywood measures 23/32, almost 1 mm less. To be sure, measure yours with calipers.

In the United States and Canada, in inches

• The sheet: 4 × 8 feet, which in inches is 48 × 96. That is 1219.2 × 2438.4 mm, almost 2440 × 1220. MDF and melamine often come slightly larger, 49 × 97, so they can be trimmed to a full 48 × 96.
• Thicknesses go in fractions of an inch: 1/4, 1/2, 5/8 and 3/4. MDF usually measures what it says; plywood does not.
• Baltic birch is made in millimetres: its “3/4” is 18 mm, and it is often sold in 60 × 60 inch sheets (5 × 5 feet).
• The saw takes 1/8 of an inch (3.2 mm) with a standard blade and 3/32 (2.4 mm) with a thin-kerf one. What that does to the plan is in the guide to saw kerf and edge trim.

Plywood in the United States, what it says and what it measures:

In inches. It is the usual for American plywood; some imported plywood is thinner still. Measure yours.

In the United Kingdom and Australia, in millimetres

In the United Kingdom the sheet is still called an “eight by four”, but it is sold in millimetres: 2440 × 1220 mm, 1.6 mm longer and 0.8 mm wider than 8 × 4 feet. The most common thickness there is 18 mm, in MDF, plywood and melamine-faced chipboard (MFC). In Australia and New Zealand the usual size is a round one: 2400 × 1200 mm.

If you work from an American plan and buy in millimetres, or the other way round, make the cut list with the sheet you are going to buy, not the one in the plan: 18 mm is not 3/4 of an inch (19.05 mm), nor 23/32 (18.26).

An example in inches: a one-sheet bookcase

An open bookcase in “3/4” plywood, 30 inches wide, 72 high and 11 3/4 deep, cut from a single 4 × 8 sheet, with a 1/8 kerf and 1/4 of edge trim:

• Side panels: full height, 72 × 11 3/4.
• Top and base: between the side panels, 30 − 2 × 23/32 = 28 9/16. Taking off 3/4 they would come out at 28 1/2, and the bookcase would be 29 15/16 wide instead of 30.
• Shelves: 1/32 less on each side, so they go in without forcing: 28 1/2.

In inches, in 23/32 plywood with the grain along the length.

Why 11 3/4 deep? The eight parts come from four strips along the sheet: 4 × 11 3/4 + 3 cuts of 1/8 = 47 3/8, and the trimmed sheet has 48 − 2 × 1/4 = 47 1/2 left. At 11 7/8 or 12 deep, four strips no longer fit and you need two sheets. At 11 3/4, the plan uses 80% of the sheet.

Try it with SliceLab

SliceLab works in millimetres or in inches: each project has its own unit, under Cutting settings, Units. In inches, you type sizes the way you would in the shop, 23 7/8, 23-7/8 or 3/4, and the plan, the report and the PDF come out in inches. The button below opens the bookcase in inches, with its kerf and its edge trim. For a single part, the parts per sheet calculator works in inches too, and the bookcase cut list calculator gives you the cut list of this bookcase in inches, or of yours with its own measurements.

You can also paste this into Import sheets and parts (CSV / Excel) in a project in inches:

Sheet;Length;Width;Quantity;Grain;Material;Thickness
S1;96;48;0;1;Plywood;23/32

Part;Length;Width;Quantity;Rotate;Grain;Material;Thickness;Edge L1;Edge L2;Edge W1;Edge W2;Sheet
Side panel;72;11 3/4;2;0;1;Plywood;23/32;1;0;1;0;S1
Top and base;28 9/16;11 3/4;2;0;1;Plywood;23/32;1;0;0;0;S1
Shelf;28 1/2;11 3/4;4;0;1;Plywood;23/32;1;0;0;0;S1

Common mistakes

• Working with 2440 × 1220 when the supplier sells 2800 × 2070, or the other way round.
• Taking off 3/4 for each side panel when the plywood measures 23/32.
• Mixing inches and millimetres in the same list.
• Swapping length and width on a sheet with grain.
• Copying the sizes from a plan from another country without changing the thickness.