Sending a letter to Canada shouldn't feel like a math problem. But honestly, if you're standing at your kitchen table with a stack of Forever stamps and a birthday card for your cousin in Toronto, it’s easy to get confused. You’ve probably heard that a standard stamp covers a letter, but that only applies to domestic mail. Once that envelope needs to cross the 49th parallel, the rules change.
How many stamps to mail a letter to Canada depends entirely on the weight of your envelope and the current rates set by the United States Postal Service (USPS). As of early 2026, the price for a standard one-ounce international letter is $1.65. If you're using the standard "Forever" stamps you bought for domestic mail—which are currently valued at $0.73 each—you can't just slap one on and hope for the best.
It won't make it. The mail carrier will likely send it back to your house with a "Postage Due" marking, or worse, it’ll just disappear into a dead-letter bin.
The Math Behind the Stamps
Let’s get into the nitty-gritty. You have two main ways to handle this. You can buy a specific Global Forever Stamp, or you can play a game of postage Tetris with domestic stamps.
The Global Forever Stamp is a round stamp that currently costs exactly what you need for a one-ounce letter to any country, including Canada. It's the "easy button." One stamp. One letter. Done. But most of us don't just have those lying around. We have the rectangular ones with flags or flowers on them.
If you're using domestic Forever stamps, you're looking at a bit of addition. Since they are worth $0.73, two of them equal $1.46. That’s not enough. You’re still short $0.19. If you put three Forever stamps on the envelope, you're paying $2.19. You’re overpaying by $0.54, but the letter will definitely get there. For some people, that fifty-cent "laziness tax" is worth not having to drive to the post office.
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Weight Matters More Than You Think
Don't assume your letter is just one ounce. A standard business envelope with three sheets of paper usually stays under that limit. But add a gift card? Or a couple of photos? Maybe a thick card with glitter and a pop-up centerpiece? Suddenly, you're in the two-ounce territory.
For every additional ounce, the price jumps. International mail isn't like domestic mail where an extra ounce is just a few cents. For Canada, a two-ounce letter currently costs roughly $2.12. If you’re pushing three ounces, you’re looking at nearly $2.60.
Go get a kitchen scale. Seriously. It saves the headache of a returned letter. If you don't have one, just know that a single heavy cardstock greeting card is almost always right on the edge of that one-ounce limit.
Why Canada is Different from Other International Destinations
It's weird, right? Canada is right there. You can practically see it from Detroit or Buffalo. Yet, the USPS treats a letter to Vancouver the same way it treats a letter to Timbuktu in terms of basic international pricing.
There used to be a tiered system where Canada and Mexico were cheaper than sending something to Europe or Asia. That’s mostly gone for basic letters. The USPS simplified the "Price Groups" years ago. Canada is technically Price Group 1, but the starting rate for a one-ounce letter remains the same $1.65 across the board for all international destinations using the Global Forever rate.
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However, if you're moving up to "Large Envelopes" (flats) or packages, being in Price Group 1 actually matters. It’s generally cheaper to send a heavy manila folder of documents to Montreal than it is to send it to Tokyo.
The Shape of the Envelope
You might think you’re being cute with a square envelope for an invitation. Don't do it. The USPS—and Canada Post once it crosses the border—uses automated sorting machines. Square envelopes don't fit the aspect ratio these machines expect.
If your envelope is square, rigid, or has a lumpy clasp on the back, it’s considered "non-machinable." This adds a surcharge. Even if it weighs less than an ounce, you'll need to add extra postage—usually around $0.46 on top of the base international rate. If you ignore this, the machine might eat your letter, or it’ll be rejected.
Avoiding Common International Mailing Mistakes
One big mistake? Using "Postcard" stamps for a letter. Postcard stamps are cheaper because postcards are smaller and lighter. But the international postcard rate to Canada is actually the same $1.65 as a letter. There is no discount for sending a postcard internationally like there is domestically.
Another issue is the address format. Canada uses a six-character alphanumeric postal code (like K1A 0B1). It’s not just numbers like our zip codes. Make sure you write this clearly. Use all caps. It helps the Canadian scanners read it faster. Also, always write "CANADA" in all caps on the very last line of the address.
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- Pro tip: Put your return address in the top left corner just like usual, but make sure to include "USA" or "United States" at the end of your own address.
What Happens When it Reaches the Border?
Your letter doesn't just go straight to your friend's house. It has to pass through a Canada Border Services Agency (CBSA) processing center. For a standard letter with just paper, this is almost instantaneous. It gets scanned and passed to Canada Post.
But if you tried to sneak a "gift" inside a standard envelope—like a small piece of jewelry or a key—customs might pull it aside. This can delay the letter by days or even weeks. If it’s more than just correspondence, you're technically supposed to fill out a customs form (PS Form 2976), even if it fits in a small envelope.
Actionable Steps for Sending Your Letter
Stop guessing. If you want that letter to arrive without drama, follow this sequence:
- Weigh your letter. If it's over 1 ounce (about 28 grams), you need more than one Global Forever stamp.
- Check for "Non-Machinable" traits. Is it square? Is it stiff? Is it lumpy? If yes, add a $0.46 cent surcharge (or an extra domestic stamp to cover the gap).
- Use the right stamps. The easiest way is one Global Forever Stamp. If you only have domestic Forever stamps, use three. Yes, you're overpaying, but it's the safest way to ensure delivery without a trip to the post office.
- Verify the address. Ensure the Canadian postal code is correct and "CANADA" is the final line.
- Drop it in a blue box. International mail can be dropped in any standard USPS collection box; you don't have to hand it to a clerk unless it's a package over a certain weight.
Standard delivery time to Canada is usually 7 to 21 days. Don't panic if it's been a week and it hasn't arrived. Cross-border mail moves at its own pace, especially during peak holiday seasons or when there are weather delays in major hubs like Chicago or Toronto.
If you need it there faster, you'll have to skip the stamps entirely and look at Global Express Guaranteed or Priority Mail International. But for a simple "thinking of you" card, three domestic stamps or one Global Forever stamp is your golden ticket.