Workshop storage unit plywood cut list: 1800mm shelving worked example

A 1800 mm tall garage shelving unit in 18 mm ply with four shelves and a 9 mm back panel needs two sheets of 18 mm ply and one sheet of 9 mm ply. That assumes a 2440 × 1220 mm (8 × 4 ft) sheet and a 3 mm saw kerf. The calculation is below.

The example unit

This guide uses a single bay of workshop shelving: 1800 mm tall, 900 mm wide, 400 mm deep. That footprint fits against a standard garage wall without protruding into the car's path. Four shelves at roughly equal spacing give clearance for tools, paint tins, hardware jars and power tool cases, which tend to cluster around 250 to 350 mm tall.

All structural parts are 18 mm birch or structural plywood. The back panel is 9 mm ply: enough to stiffen the unit against racking without adding unnecessary weight. MDF is not used here because workshop storage gets damp, knocked and occasionally wet, and MDF does not recover from that.

Parts list

The carcass is built as a box: two full-height sides, a top and bottom fitting between the sides, and four internal shelves. The sides set the overall height at 1800 mm and depth at 400 mm. The top, bottom and shelves fit between the sides, so their width is the overall width minus two panel thicknesses: 900 minus 2 × 18 = 864 mm.

The shelves are 6 mm shallower than the sides to leave a channel for the back panel: 400 minus 9 minus 6 = 385 mm (the 6 mm gap at the front edge allows the back to sit flush with the rear of the carcass without the shelves obstructing it). Top and bottom are the full 400 mm depth.

How the 18 mm parts nest onto sheets

There are eight 18 mm parts in total: two sides, one top, one bottom and four shelves. Here is how they fit onto two sheets of 2440 × 1220 mm ply.

Sheet 1 (2440 × 1220 mm, 18 mm ply):

• Side panel A: 1800 × 400 mm. Place it along the length of the sheet, using 1800 mm of the 2440 mm length and 400 mm of the 1220 mm width.
• Side panel B: 1800 × 400 mm. Place it alongside A. Two panels at 400 mm each plus one 3 mm kerf use 803 mm of the 1220 mm width. The remaining 417 mm strip is 2440 mm long.
• Top panel: 864 × 400 mm. Cut from the 417 mm strip remaining after the two sides. Place it at the end of the sheet: 864 mm of the 2440 mm length, 400 mm of the 417 mm strip width. Fits with 17 mm to spare in width (417 minus 400 = 17 mm, enough to get a clean kerf).
• Bottom panel: 864 × 400 mm. Placed next to the top panel in the same strip. Together the top and bottom use 864 + 3 + 864 = 1731 mm of the strip length, leaving 2440 minus 1731 = 709 mm of strip for offcut.

Sheet 1 gives both sides, the top and the bottom. The strip offcut (709 × 417 mm) is useful for workshop brackets or can be discarded.

Sheet 2 (2440 × 1220 mm, 18 mm ply):

• Four shelves: each 864 × 385 mm. Laying them side by side across the 1220 mm width: four shelves at 385 mm each plus three kerfs at 3 mm each = 1540 + 9 = 1549 mm. That exceeds the 1220 mm sheet width.
• Run them in two rows instead: two shelves across the width (385 + 3 + 385 = 773 mm, within the 1220 mm width) and two rows of 864 mm along the length (864 + 3 + 864 = 1731 mm, within the 2440 mm length). All four shelves fit within a 1731 × 773 mm area, comfortably inside one sheet.

Sheet 2 gives all four shelves. The remaining area of sheet 2 (approximately 2440 × 447 mm across the bottom, plus the top strip) is useful offcut for a future project or for adding a fifth shelf later.

Total 18 mm ply: 2 sheets.

The 9 mm back panel

The back panel is 1800 × 900 mm. A standard sheet is 2440 × 1220 mm, so the back fits on one sheet with 640 mm of length and 320 mm of width remaining as usable offcut. There is no need for a join.

Total 9 mm ply: 1 sheet.

Quick area check

Total area of the eight 18 mm parts:

• 2 sides: 2 × (1800 × 400) = 1,440,000 mm²
• Top + bottom: 2 × (864 × 400) = 691,200 mm²
• 4 shelves: 4 × (864 × 385) = 1,330,560 mm²
• Total: 3,461,760 mm²

One sheet: 2440 × 1220 = 2,976,800 mm². Dividing: 3,461,760 / 2,976,800 = 1.16. Add 20% for kerf and waste: 1.40. Round up: 2 sheets. Agrees with the nesting above.

Shelf spacing options

The four shelves divide the 1800 mm height into five bays. With a top and bottom each using 18 mm, the internal height is 1800 minus 36 = 1764 mm. Four shelves at equal spacing give bays of approximately 1764 / 5 = 352 mm each, which suits most workshop storage. The shelf positions shown below are a starting point; adjust to match your tallest items.

The 334 mm clear opening (shelf thickness of 18 mm subtracted from the 352 mm bay) fits a standard one-litre paint tin standing upright (typical height around 285 mm). For deeper power tools or stacked items, drop one shelf and use 420 mm bays instead.

Scaling to multiple bays

A double-width unit (1800 mm wide) doubles the top, bottom and shelf widths. At 1764 mm per shelf, they no longer fit beside a side panel on a single sheet. The sheet count scales roughly as follows:

Multiple bays sharing a common back panel can save one sheet of 9 mm ply if you run a continuous back across all bays rather than cutting separate panels per bay.

UK sheet sizes and where to buy

The standard UK sheet is 2440 × 1220 mm, the metric near-equivalent of the 8 × 4 ft sheet used in the US and Canada. All calculations above use this size. For US readers: 2438 × 1219 mm is near enough that the cut list works without adjustment.

For workshop storage, the cheapest grade of structural ply that takes screws cleanly is the right choice. C/C or C/D face grades are widely available at Travis Perkins, Wickes and independent timber merchants, and they are more than adequate for a storage unit that no one will look at face-on. Birch ply machines more cleanly but costs roughly twice as much for no structural benefit in this application.

Most larger merchants offer a sheet-cutting service. For this project, getting both the 18 mm sheets ripped to 400 mm wide at the yard saves the most time, as the long rip down the side panels is the hardest cut to make accurately at home.

Plan your own cut list

The dimensions above are for a 1800 × 900 × 400 mm unit. If yours is a different size, the method is the same: list every part, calculate the finished size accounting for ply thickness, nest the parts onto sheets, and allow for kerf.

SawReady does the nesting and sheet-count arithmetic for you. Enter your parts, set your sheet size and kerf, and it produces the most efficient layout and a sheet count you can take to the yard.

Plan your storage unit cuts