What Size Should a Poster Be? Standard Poster Dimensions in Canada

A grad student came into the shop last spring with a research poster due at a conference in three days. She'd designed the whole thing at 30x40 inches — a size that looked fine on her laptop but fit no display board her conference actually used, and the file was built at 72 DPI so the text turned to mush the moment we scaled it up. We rebuilt it to 48x36 landscape at proper resolution and got it printed with a day to spare, but it was a stressful 72 hours that a five-minute size check would have prevented.

That's the thing about poster sizes: the wrong one doesn't announce itself until you're at the finish line. This guide lays out the standard poster sizes we print every week in Ottawa — in both inches and millimetres — plus how to think about aspect ratio, resolution, and bleed so your file prints sharp the first time.

There's no single "correct" poster size. There's a short list of standard poster sizes that exist because frames, display boards, and printing presses were built around them. Pick one of those and everything downstream — framing, mounting, shipping — gets easier and cheaper. Pick a random size and you inherit a custom-framing headache.

The standard poster sizes, in inches and mm

Here are the sizes that cover roughly 95% of the posters we print. The North American inch sizes (top group) dominate retail, events, and Canadian academic work; the ISO A-series (bottom group) shows up for international conferences and design work that follows European standards:

One size not in the table but worth knowing: the movie one-sheet at 27x40 in (686 x 1016 mm). It's a great-looking format, but almost no retailer stocks a 27x40 frame, so budget for custom framing if you go that route. For a full breakdown of paper stocks and lamination, see our large-format poster printing guide.

How to pick a standard poster size

The right size comes down to three questions: where it hangs, how close people stand, and whether it needs to fit a ready-made frame.

• 18x24 — the safe default. Widest selection of off-the-shelf frames of any poster size, close to photo proportions, big enough to read across a room but not so big it dominates. When someone asks us what size a poster should be with no other constraints, this is the answer.
• 24x36 — when you need presence. The standard large advertising and trade-show poster. Great for retail windows, event backdrops, and anywhere the poster is the main visual. Still framable off the shelf, just pricier.
• 11x17 / 12x18 — small and cheap to run. Ideal for community event posters, class projects, and window bills where you want quantity without a big per-piece cost.
• A0 / A1 — the metric world. If your conference or client specs A-series, stay in it. Don't convert an A0 design to 33x47 inches and hope; small rounding differences cause white slivers at the trim.

Portrait vs landscape is just the same size rotated — 24x36 portrait vs 36x24 landscape. Retail wall art and movie posters lean portrait; academic conference posters are almost always landscape (48x36) so they fit the display boards. When in doubt, match the orientation of your dominant image.

Aspect ratio: why some sizes are "friendlier"

Aspect ratio is the relationship between width and height, and it decides how much of your image survives when it's placed on a given size. The North American standards — 18x24 and 24x36 — sit near 3:4 and 2:3, the same neighbourhood as most camera photos, so a full-bleed photo fills them with minimal cropping.

The ISO A-series is the clever one. Every A size — A0, A1, A2 and down — shares a constant 1:√2 (about 1.414) ratio. Cut an A0 in half and you get two A1s with the identical proportions. That means artwork scales up or down the whole series without distortion or re-cropping, which is exactly why it's an international standard. If you want the underlying math, Wikipedia has a clear rundown of the ISO A-series and North American paper size standards and a good primer on image aspect ratio.

The practical takeaway: choose a poster size whose ratio matches your key image, not the other way around. Forcing a wide landscape photo onto a tall portrait poster means either cropping out half the shot or leaving dead bars top and bottom.

Resolution and DPI for large format

Posters are big, so people worry they need enormous files. Not quite. Resolution needs to be high enough for the distance people actually stand — and the bigger the poster, the farther back they usually are.

• 300 DPI up to 24x36. Posters you read up close (retail, photo art, small signage) should be built at 300 dots per inch. A 24x36 at 300 DPI is 7200 x 10800 pixels.
• 150-200 DPI for larger. On A1, A0, and big trade-show pieces viewed from a metre or more away, 150-200 DPI looks identical to 300 to the naked eye — and keeps the file manageable.
• Vectors don't have DPI. Logos and text built as vector art stay razor-sharp at any size. If your artwork is pixel-based and low-res, our vectorization service can rebuild it clean.

If you're unsure what a file can handle, send it over — we'll tell you the largest size it prints sharp before anything goes to the press. For the underlying concept, here's a solid reference on dots per inch (DPI) resolution.

Bleed and safe zone: don't skip this

This is the most common reason a poster comes back with a thin white line along one edge. Bleed is artwork extended past the trim line so that after the cutter runs, there's no unprinted paper showing. Standard bleed is 0.125 in (3.175 mm) per side — which means you add 0.25 in (6.35 mm) total to both the width and the height of your document.

So a finished 24x36 poster is built as a 24.25 x 36.25 in file, with the background pushed all the way to those outer edges. Then there's the safe zone: keep all critical text, logos, and anything you can't afford to lose at least 0.25 in inside the trim line, because cutting has a small tolerance. Here's a plain-language explainer of what bleed means in printing if you want the full picture. The same rules apply to smaller print jobs — our flyer sizes and paper guide walks through bleed on flyers too.

What poster printing costs in Canada

Rough 2026 Canadian retail ranges so you can budget. Your exact price depends on paper stock, finish, and quantity — bulk runs drop the per-piece cost fast:

• 18x24 glossy: about $15-$30 CAD each for one-offs.
• 24x36 matte: about $20-$50 CAD each.
• Academic 36x48 research poster: paper from ~$30-$50 CAD; fabric (travel-friendly, folds into a suitcase) around $70 CAD. For reference, the University of Waterloo lists a 48x36 matte at $72 plus tax and glossy at $114 plus tax.

A quick note on Canadian sizing history: Canada once had its own P-series (P1-P6) paper standards, but you'll almost never encounter them today. Modern Canadian poster printing runs on North American inch sizes (18x24, 24x36, 27x40) or the ISO A-series — so build in one of those and you're safe. Want an exact number for your job? Grab a free mockup and quote below, or browse our signs and large-format printing options.

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