Choosing the wrong thickness is the second most common plywood mistake after choosing the wrong grade. Too thin and shelves sag and carcasses wobble; too thick and you pay for weight and material you did not need. These are common starting points used by carpenters and designers — always check against your own spans and loads.
6 mm — backs and light panels
Cabinet and wardrobe backs, drawer bottoms in small drawers, and light decorative panelling fixed to a frame.
10–12 mm — drawers and partitions
Drawer sides and bottoms, light partitions, ceiling and wall panelling, and small shelves with short spans.
18 mm — the everyday standard
The most used thickness for furniture: wardrobe and kitchen carcasses, shutters, beds, TV units and office furniture. If you are unsure, 18 mm is the usual choice for anything that carries load.
22–25 mm — heavy loads and long spans
Long shelves, table tops, heavy-duty storage, counters and furniture that must feel solid. For long shelves that must not sag, also consider block board.
Up to 35 mm — heavy-duty work
Extra-thick plywood for heavy worktops, platforms and special joinery where strength and stiffness matter most. Duro plywood is available from 6 mm up to 35 mm, and Duro flush doors up to 38 mm.
Measure before you buy
A sheet sold as 18 mm should measure close to 18 mm. Under-thickness sheets are one of the most common ways cheap plywood cuts cost — measure at more than one point before you buy.
