Aspect Ratios for Greeting Cards

A few independent artists have asked questions about how their artwork is fit onto Greeting Cards and how they will look when they’re printed. So here's some helpful advice from a fellow independent artist on the Redbubble marketplace, Rick Grundy.

Character Limits

For Postcards, there is a 35-character limit, as opposed to the Greeting Cards, which have a 40 character limit. Your artist information will be placed on the backside of each style card.

How will my art look on the cards?

That depends on the aspect ratio of your images. An aspect ratio of three to t—
Hang on...

What’s an Aspect Ratio?

Aspect ratio is a mathematical way of describing how rectangular a rectangle is in terms of its width and height. A square box’s sides will always be the same length as each other – we’d say that it was “1:1”. By that same logic, we’d call two boxes side by side forming a long, thin rectangle “2:1”.


We could make those same rectangles using more boxes (let’s call those boxes pixels from now on).


We'll use cameras as an example from now on because it’s what comes naturally, but exactly the same principle applies to flatbed scanners, vector graphics software, fractal generators, or any of the other myriad ways of producing a file on your desktop that ends in .jpg or .png.

Your digital camera might take photos at 2660×2000 pixels. No one likes saying twenty-six-thousand-and-sixty by two-thousand so we’ll use what little maths we can remember from high school to simplify that fraction to “4:3”.

The two most common camera formats these days are 3:2 (Canon and Nikon digital SLRs and 35mm film) and 4:3 (most compact digital cameras).


If you’re not sure what format your camera produces there’s an easy way to find out. Check the resolution of one of your photos and divide the width by the height. 1.33 = 4:3, 1.5 = 3:2. For example, a 10 megapixel Canon 40d shoots at 3888×2592. 3888/2592 = 1.5, so all of its images will be a 3:2 ratio when they come off the camera.

Incidentally, 3888 multiplied by 2592 is just about 10 million which is where the whole 10-megapixel business comes from; but that’s a story for another day.

Fascinating stuff, tell me more!

No chance! If you’re interested in the history and intricacies of this nonsense then the Wikipedia article is a good place to start.

Fair enough. How does this affect me as a card designer?

Cards are printed by 3rd-party printers at either 4×6 inches or 5×7.5 inches, which by now should be leaping out as an aspect ratio of 3:2 (or 2:3 if you’re designing a portrait card; it’s the same rectangle).

There are three basic scenarios depending on the shape of your uploaded images:

I shoot at 3:2, or crop to 3:2 before uploading

Common practice! And that's the simplest situation to deal with. Because these images are the same shape as the card itself there's no need to modify them at all to print right up to the edges. Now, this is not an exact science, which means an image that is “close enough” to a 3:2 ratio may fill the entire card. But your safest bet is to simply follow the 3:2 golden rule.


My camera or scanner produces 4:3 photos

OK, now this is a little bit more complicated. The whole of your design can't be fit onto the card without leaving a border on at least two edges, so instead, a slight crop will be added to remove the parts of your image that don’t fit.


On the landscape card in the stunning diagram above the top and bottom will be cropped (exaggerated for dramatic effect; you’ll really only lose a few millimeters), while a portrait card will crop the left and right edges. An equal amount will be automatically trimmed from both sides if you upload a 4:3 file, but you can always choose your own window by manually cropping your images to 3:2 before you upload them.

My art is an unusual shape. What about panoramas and squares?

The amount of cropping needed to fill the card with a long and thin or almost square image would remove a significant amount of your work – and it's fair to assume that you designed it that way for a reason. In these cases, a border will be added around the art and the whole image will be printed, just like a matted print.


Fantastic! Then all – or almost all – of my artwork will be printed on the card?

If the magic software detects that your card will look best with borders then yes; 100% of your image will be printed.

In the printing industry, borderless designs are produced by printing on a larger sheet than the final product and then cutting off the bleed ink. The printers used only need to trim off 2.5mm (0.1in) bleed which you’ll barely notice, but if you have a one-pixel black border around the edge of your design you shouldn’t be surprised if it doesn’t show up on the finished card.

Additionally, it is best practice to ensure that 5-6mm from the edge is free of important design elements (logos, images, etc) and text. 

We’ve tried to simulate this on the updated card previews, and they’ll give you and your buyers a fairly accurate idea of what the final product will look like.

One last thing. What’s the minimum resolution of image that I can sell as a card?

That hasn’t changed – to support all of the awesome cards that have been designed over the last three years it’s still 1300×900 pixels. That’s somewhere between a 3:2 and 4:3 aspect ratio (and that confusion is one of the reasons the shape of the cards was changed), so if you upload at that exact size, a tiny bit off the edges will now be cropped to give you a borderless print.