MDF vs plywood: which should you use?

Both are sold as flat sheets in the same thicknesses, which makes them easy to mix up on a materials list. They behave very differently once you're cutting, joining and finishing them.

What each material actually is

MDF (medium-density fibreboard) is made from wood fibres broken down and re-bonded with resin under heat and pressure. There's no grain and no layering — it's uniform all the way through, which is exactly why it cuts and machines so cleanly. Plywood is the opposite construction: thin veneers of real wood glued together with the grain direction alternating in each layer, which is what gives it its strength.

Strength and screw-holding

Plywood's cross-layered structure makes it strong for its weight and resistant to splitting, and it holds screws well even close to an edge. MDF is dense but has no long fibres running through it, so it's more brittle at edges and corners, and screws driven into the edge or into thin MDF (below around 12mm) tend to blow out unless you pre-drill and use the right screw for the job. For anything load-bearing or subject to repeated racking — a shelf that gets loaded and unloaded, a drawer box, a piece that gets moved — plywood is generally the safer choice.

Moisture

Standard MDF absorbs moisture readily and swells, especially at cut edges and corners where the fibres are exposed — it's not a good choice for anywhere it might get damp (bathrooms, exterior work, anywhere near a sink) unless you're using a moisture-resistant (MR) grade and sealing every cut edge. Plywood has better inherent moisture tolerance because of its layered structure, and exterior/WBP (weather and boil-proof) grades are made specifically for damp or outdoor use.

Finish and appearance

This is where MDF wins outright for painted work: it has no grain, no voids, and takes paint and primer beautifully, which is why it's the standard choice for painted cabinetry, skirting, architrave and moulded profiles. Plywood shows its edge layers when cut (the "ply lines"), and its face grain telegraphs through paint unless you fill and sand carefully — it's much better suited to a natural or stained finish where the grain is part of the look, or to structural work that gets covered or painted roughly rather than finished to a fine standard.

Dust and cutting

MDF produces very fine dust when cut or sanded, finer than most timber dust, so good extraction and a proper dust mask matter more than usual. Plywood's alternating grain can cause splintering on the underside of a cut, particularly with a blunt or wrong-toothed blade — a fine-tooth blade, or scoring the cut line first, gives a cleaner edge, especially on veneered or good-face ply.

A rough rule of thumb

Choose MDF for anything that will be painted, doesn't need to survive damp, and doesn't take heavy repeated load at a thin edge — cabinet doors, painted furniture, mouldings, shelving that's well-supported along its length. Choose plywood for anything structural, anywhere strength-to-weight matters, drawer boxes and carcasses, or anywhere it might get damp.

Once you know which material suits your project, use the Boardwise estimator to work out how many sheets you'll need and what it'll cost.