---
title: "Canada Post size requirements for postcards and letters"
description: "Canada Post's standard size is 140 × 90 mm to 245 × 156 mm, up to 5 mm thick and 50 g. The limits for postcards, letters, and oversize mail."
canonical: https://trysincerely.com/guides/canada-post-size-requirements
last_updated: 2026-10-11
---
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# Canada Post size requirements for postcards and letters

> Canada Post's standard size is 140 × 90 mm to 245 × 156 mm, up to 5 mm thick and 50 g. The limits for postcards, letters, and oversize mail.

Source: https://trysincerely.com/guides/canada-post-size-requirements

A standard Canada Post postcard or letter measures between 140 × 90 mm and 245 × 156 mm, is no more than 5 mm thick, and weighs 2 g to 50 g. Anything larger, up to 380 × 270 mm, 20 mm thick, and 500 g, mails as non-standard or oversize at a higher price. Past those limits it becomes a parcel. Both common US postcard sizes, 4×6 and 6×9, fit the standard band. Cards and postcards mailed from Canada to the US or abroad have a lower ceiling of 235 × 120 mm, which a 6×9 card exceeds. These figures come from Canada Post's [Lettermail size requirements](https://www.canadapost-postescanada.ca/cpc/en/support/articles/lettermail/size-requirements.page) and its [letter size and weight limits](https://www.canadapost-postescanada.ca/cpc/en/support/kb/sending/sending-faq/how-big-or-small-can-a-letter-be.page), both read on October 10, 2026.

![A to-scale drawing: a 4×6 and a 6×9 postcard both fit inside the 245 × 156 mm standard box, up to 50 g, which sits inside the 380 × 270 mm oversize box, up to 500 g.](https://trysincerely.com/images/guides/canada-post-size-requirements.webp)

*Under Canada Post size requirements, both common US postcard sizes mail at the standard price inside Canada, and anything larger up to 380 × 270 mm is oversize.*

## Lettermail sizes

Lettermail is the stamped service: one stamp on an envelope or a postcard. Canada Post sorts it into two size bands.

| Band                      | Minimum     | Maximum      | Thickness       | Weight                                        |
| ------------------------- | ----------- | ------------ | --------------- | --------------------------------------------- |
| Standard                  | 140 × 90 mm | 245 × 156 mm | 0.18 mm to 5 mm | 2 g to 50 g                                   |
| Non-standard and oversize | 140 × 90 mm | 380 × 270 mm | up to 20 mm     | 3 g (non-standard) or 5 g (oversize) to 500 g |

Canada Post's [stamp price page](https://www.canadapost-postescanada.ca/cpc/en/personal/stamp-prices.page) translates the weight limits into paper: about 5 sheets of paper stay under 30 g, and about 9 sheets stay under 50 g. A one-page letter in a plain envelope stays well inside the lowest step.

## Personalized Mail sizes, for bulk addressed mail

Bulk B2B mail usually goes as Personalized Mail, which Canada Post sorts on machines. Its [Smartmail Marketing customer guide](https://www.canadapost-postescanada.ca/cpc/doc/en/support/customer-guide/smartmail-marketing.pdf), effective March 23, 2026, repeats the Lettermail limits and adds rules about shape and stock.

| Machineable item  | Length | Width  | Thickness | Weight |
| ----------------- | ------ | ------ | --------- | ------ |
| Standard, minimum | 140 mm | 90 mm  | 0.18 mm   | 2 g    |
| Standard, maximum | 245 mm | 156 mm | 5 mm      | 50 g   |
| Oversize, minimum | 140 mm | 90 mm  | 0.5 mm    | 10 g   |
| Oversize, maximum | 380 mm | 270 mm | 20 mm     | 500 g  |

For a standard item, the length divided by the width has to fall between 1.3 and 2.6. A postcard or card needs stock of at least 160 gsm, which the guide puts at about 60 lb cover. An envelope needs at least 75 gsm and a folded self-mailer at least 90 gsm. Standard items must be paper and flexible enough to bend, with no plastic wrap. Die-cuts on the top, leading, or trailing edge, unusual sealing, and decorative fonts need Canada Post's testing and approval before deposit. Square envelopes from 140 mm to 156 mm a side are accepted, but square cards and self-mailers also need testing first.

## Where common US sizes land in Canada

US print sizes are quoted in inches. Converted at 25.4 mm to the inch, the familiar formats fall into Canada Post's bands like this.

| Format                        | Size in mm | Aspect ratio | Canada Post band |
| ----------------------------- | ---------- | ------------ | ---------------- |
| 4×6 postcard                  | 152 × 102  | 1.5          | Standard         |
| 6×9 postcard                  | 229 × 152  | 1.5          | Standard         |
| #10 envelope (9.5 × 4.125 in) | 241 × 105  | 2.3          | Standard         |
| 6×11 postcard                 | 279 × 152  | 1.8          | Oversize         |
| 9×12 envelope                 | 305 × 229  | 1.3          | Oversize         |

The 6×9 postcard surprises people. It is a large card in the US, yet a 229 × 152 mm card fits inside Canada Post's 245 × 156 mm standard box, so inside Canada it mails at the standard price. Mailed from Canada to a US address, the same card is over the 235 × 120 mm limit for cards, while a 4×6 card is under it.

## Where the address and postage go

The same customer guide fixes zones on the address side of each piece, and the zones differ between standard and oversize items. Canada Post can apply surcharges or delay a mailing whose address block sits outside them.

On a standard item, such as a 4×6 or 6×9 postcard or a letter in a #10 envelope:

- Postage takes the top-right corner, a zone 74 mm wide and 35 mm high, or 100 mm wide when a postage meter prints it.
- The whole destination address sits at least 35 mm below the top edge and 10 mm inside the bottom, left, and right edges.
- Leave 5 mm around the address block clear of text, graphics, and dark colors.
- Put the return address above the destination address, in the same orientation, with at least 15 mm between them.

On an oversize item, such as a 6×11 postcard or a 9×12 envelope, the address zone starts one quarter of the item's height below the top edge, the clear space is 6 mm above the address block and 10 mm on its sides and below it, and the return and destination addresses sit at least 18 mm apart.

On Personalized Mail of either size, a printed return address must be Canadian.

- Print the address in a dark, plain font. Canada Post rules out shadow and emboss effects, uneven character heights, and calligraphy styles.

Canada Post's [addressing rules](https://www.canadapost-postescanada.ca/cpc/en/support/articles/addressing-guidelines/important-information.page) add the line rules: characters 2 mm to 5 mm tall in one font, every line under 40 characters not counting spaces, and two spaces between the province and the postal code.

## How Sincerely sizes Canadian mail

Sincerely prints 4×6 and 6×9 postcards and one-page letters for Canadian recipients from the same print files it uses for US mail, then mails them inside Canada as Personalized Mail. A design does not change size or layout when its recipient is in Toronto instead of Chicago. Both postcard sizes cost the same 9 credits in Canada, and a letter costs 10. To choose a service for your list, read [B2B direct mail in Canada](https://trysincerely.com/guides/direct-mail-in-canada). The postage for each size is on [Canada Post direct mail rates](https://trysincerely.com/guides/canada-post-direct-mail-rates).

## Related questions

- [B2B direct mail in Canada: which Canada Post service fits](https://trysincerely.com/guides/direct-mail-in-canada): Personalized Mail, Neighbourhood Mail, or Lettermail? Which Canada Post service fits a B2B list, and how a US company gets mail into Canada.
- [Canada Post direct mail rates for 2026, in CAD](https://trysincerely.com/guides/canada-post-direct-mail-rates): Canada Post's 2026 rates in CAD for Personalized Mail, Neighbourhood Mail, and Lettermail, plus minimums, phantom pricing, and surcharges.
- [Postcard or letter, which should you send?](https://trysincerely.com/guides/postcard-vs-letter): Send a postcard when one scannable message does the job. Send a letter when you need room, formality, or privacy. Decision rules with current format costs.
- [What is a self-mailer?](https://trysincerely.com/glossary/self-mailer): A self-mailer is a folded printed piece that mails without an envelope. USPS rules, costs, and use cases compared to postcards and letters.
- [Canada Post strike status: is Canada Post delivering?](https://trysincerely.com/guides/canada-post-service-disruptions): As of October 11, 2026, Canada Post is delivering with no strike. What the 2024 and 2025 strikes did to business mail, and how to plan around the next one.
- [USPS size requirements for postcards and letters](https://trysincerely.com/guides/usps-mail-size-requirements): A USPS postcard runs 3.5 × 5 in to 4.25 × 6 in with a stamp, or up to 6 × 9 in mailed commercially. Letter, flat, thickness, and aspect ratio limits.

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Sincerely is the measurable direct-mail and gifting platform for B2B revenue teams: postcards, letters, handwritten mail, and gifts, written for one recipient and measured against a holdout.

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