Postcard Sizes: A Practical Guide for Direct Mail

4×6 in — the workhorse. Cheapest per piece, cheapest to mail, and enough room for one clear offer with a strong image. This is the right size for a high-volume neighbourhood drop where the goal is reach rather than depth. The constraint is real though: at 4×6 you get one message, not three.

5×7 in — the best default for most businesses. Noticeably more present than a 4×6 in a stack of mail, with enough room for an offer, supporting detail, and a proper call to action. If you are unsure, start here.

6×9 in — genuinely hard to ignore. It physically stands out in a handful of mail and gives you room to run something closer to a mini-flyer. Costs more per piece and may fall into a higher postage tier, so it is best used for higher-value offers where a lower response rate still pays.

Two others worth knowing: 4×9 in (a rack-card shape that fits a standard envelope and display racks) and 6×11 in (large-format, real impact, highest cost).

This is the part people discover too late. Mail rates are banded by dimensions and thickness, and crossing a band boundary by a few millimetres can raise the cost of every single piece in a 5,000-unit mailing.

Because postage usually costs more per piece than printing does, the mailing rules should drive the size decision rather than the other way around. A 6×9 that lands in a higher band can cost meaningfully more to distribute than a 5×7 that does not — often enough to fund a larger print run at the smaller size.

Check the current rules before you commit. Canada Post publishes dimensional and thickness limits for each mail category, and these change. If you are running an unaddressed neighbourhood drop, the rules differ again from addressed mail. Confirm your specific size, weight and thickness against the service you are actually using — we can print to any size, but we cannot tell you what a given carrier will charge on the day.

Thickness matters too, not just length and width. A heavy card stock on a large postcard can push a mailing into a different category on thickness alone.

Postcards are normally printed on cover stock rather than text weight — commonly 14pt or 16pt. Anything thinner feels flimsy and arrives creased; a postcard that bends in the mail has already lost.

Gloss makes photography and colour pop and resists moisture, which matters for anything going into an exterior mailbox in an Ottawa winter. The downside is that you cannot write on it reliably.

Matte or uncoated reads as more considered and can be written on, which is worth a lot if you want to add a handwritten note — a genuinely effective tactic for local service businesses.

UV coating on one side only is the practical compromise: gloss on the image side for impact, uncoated on the address side so it takes pen and print cleanly. Say so when you order, because a full gloss both sides is the usual default.

If the postcard is being mailed, the address side is not free space. Carriers need a clear zone for the address block and any barcoding, and design encroaching into it can get a mailing rejected or surcharged.

Practical guidance: keep the right-hand portion of the address side clear, leave the bottom strip free for barcoding, and do not run background colour or imagery through those areas. Confirm exact clear-zone dimensions with whoever is handling the mailing before you finalise the layout.

Standard bleed and safe-area rules apply on both sides — 3 mm of bleed, and text kept 3 mm inside the trim.

The most common mistake is treating a postcard as a small brochure. It is not. A postcard gets somewhere between one and three seconds of attention while someone stands over a recycling bin, and everything on it has to earn its place in that window.

Front:one image, one headline, one offer. The headline should be legible at arm’s length without effort. If a passer-by cannot tell what you sell and why they should care in two seconds, the design has failed regardless of how good it looks.

Back:the detail — what you do, how to reach you, and a specific call to action. “Call for a free quote” beats “visit our website” for most local service businesses because it asks for a smaller commitment.

Give people a reason to keep it. A dated offer, a discount code, or something genuinely useful (a fridge-magnet-style reference, a seasonal reminder) dramatically outperforms a general awareness card. Tracking matters too — a distinct phone extension, a code to mention, or a dedicated landing page is the only way to know whether the drop worked.

Postcards win when the message is short, you are mailing, and you want something durable. Card stock survives handling, does not need an envelope, and gets read without being opened — which is its single biggest advantage over anything folded or enveloped.

Flyers win when you have more to say, are hand-distributing rather than mailing, or need a lower per-piece cost at high volume. See our flyer size and paper guide for that side of the decision.

Door hangers are the third option and are underrated for local trades — they cannot be missed the way something pushed through a letterbox can, and they sidestep mail costs entirely.