Poster frame sizes and what they fit

Poster framing has one problem that ordinary picture framing does not: posters are printed to advertised sizes that the paper does not always honour. A 24x36 poster is often 23.75 x 35.75. A movie one-sheet described as 27x40 is regularly 27x41. Before anything else in this guide is useful, measure the sheet you actually own.

The standard poster sizes

Internationally the equivalents are A3 (11.7 x 16.5 in), A2 (16.5 x 23.4 in), A1 (23.4 x 33.1 in), 30x40 cm, 50x70 cm and 70x100 cm. None of these convert cleanly into US sizes, which is the single biggest source of poster framing frustration for anyone buying prints from European sellers.

The sizes shops actually stock

18x24 and 24x36 are available in any general store. 27x40 is available anywhere that sells movie memorabilia. Everything else — 12x18, 20x30, 22x28, 30x40 — is an online or specialist purchase. This is worth knowing before you commit to a poster size, because a print that costs fifteen dollars can easily need a forty-dollar special-order frame.

Weight is the real constraint

A poster frame is mostly glazing, and glazing is where the weight is. Approximate weights for a 2mm float glass sheet against 2mm acrylic:

Add the moulding, backing and hardware and a glazed 24x36 wooden frame lands around 11 to 13 pounds. That needs a proper wall fixing — a stud, a toggle, or two hooks rated well above the load — and it needs the frame's own joints to be strong enough not to rack under their own weight.

For posters specifically, acrylic wins nearly every time. Posters are reproducible. The scratch resistance of glass is not worth eight pounds hanging over a sofa.

Matting a poster

Below 24x36, a mat transforms a poster. It separates a mass-produced image from the wall, gives it a border the design was probably never given, and makes the whole thing read as a deliberately hung object rather than a thing taped up in a dorm.

Standard pairings:

• 11x17 poster in a 16x20 frame
• 12x18 poster in an 18x24 frame
• 16x20 poster in a 20x24 or 22x28 frame
• 18x24 poster in a 22x28 or 24x30 frame
• 24x36 poster in a 30x40 frame

Above 24x36, matting starts to cost more than the poster and demands wall space most rooms do not have. At that point full-bleed is the sensible choice.

Snap frames and clip frames

Two categories exist that ordinary picture framing does not have.

Snap frames — sometimes called poster snap frames — have four hinged aluminium edges. You flip them open, drop the poster on the backing behind a clear styrene sheet, and snap them shut. Changing a poster takes fifteen seconds. They exist for retail and cinema display, they look exactly like what they are, and if your poster changes monthly they are the correct answer regardless of aesthetics.

Clip frames are a sheet of glass or acrylic and a backing board held together with spring clips at the edges, with no moulding at all. They are cheap, they look minimal, and the exposed glass edges chip. Acceptable for temporary display; not something to trust with anything you would be upset to damage.

Framing a poster without damaging it

Three rules, in order of how often they are broken.

Never trim a poster to fit a frame. It permanently destroys any collectible value, and a trimmed edge is always visible up close. If the poster is slightly too large, the frame is wrong, not the poster.

Let a rolled poster relax first. Unroll it, lay it flat under a few heavy books with clean paper between, and leave it a day or two. Forcing a curled poster into a frame builds in a permanent bow that presses the centre against the glazing.

Do not dry-mount unless you are certain. Dry-mounting bonds a poster permanently to a board. It gives a perfectly flat result and it is irreversible. For a reproduction you will replace in three years, fine. For anything signed, limited, or older than you are, do not.

Hanging a large poster frame

At 24x36 and above, take the hanging seriously.

• Use two fixings, not one. Two hooks spaced roughly a third of the frame width apart stop the frame rotating and let you level it precisely.
• Find a stud where you can. Where you cannot, use toggle bolts or self-drilling anchors rated at least three times the frame's weight.
• Hang the centre of the image at about 57 to 60 inches from the floor — gallery eye level.
• Add adhesive bumpers to the bottom corners so the frame sits off the wall, hangs straight, and does not trap dust behind it.

The full method, including the paper-template trick for multiple frames, is in the guide to hanging a picture frame.

Measuring a poster properly

Because printed poster sizes drift from their advertised ones, measuring is not optional.

Lay the poster flat and measure both dimensions at two points each — top and bottom, left and right. Posters are frequently cut slightly out of square, and the figure you need is the largest measurement in each direction, since that is what has to fit inside the frame.

If the poster measures within an eighth of an inch of a standard size, a standard frame will hold it. Between an eighth and half an inch under, it will fit but may shift — a couple of pieces of archival tape at the top corners, attaching it to the backing board, solves that. More than half an inch under, and it needs a mat to look intentional.

If it measures over a standard size in any direction, the frame is wrong. Do not trim it.

Cost, relatively

For a reproduction poster, the first two rows are usually the right answer. Custom framing a poster costs several times what the poster did, which is worth it only when the poster is genuinely collectible.