Understanding aspect ratio is an important part of cropping, resizing, and ultimately printing photographs. It’s a key element to getting an image to fit to a specific shape. Aspect ratio is jargon for shape. It’s a way to describe how the width of an image relates to its height.
Let’s start off easy, with a square. The height and width of squares are equal. For every unit of height (pixel, inch, centimeter, etc.) there’s an equal unit of width. This is a one to one relationship.
A square aspect ratio is expressed as 1:1. Wow, easy.
Wreck-tangles ruin everything
Rectangles don’t have equal sides; one is always longer than the other. If the image is twice as wide as it is high, then the ratio between width and height is two to one. This is expressed as a 2:1 aspect ratio.
2:1 isn’t a super common shape, but sticking two squares together is useful for conceptualizing and getting use to units of measurement.
What’s a more common aspect ratio?
A more common shape for image editing is 2:3, which you might sometimes see expressed as 3:2. The order of the numbers aren’t super important; it’s their relationship that matter. 2:3 and 3:2 are the same ratio.
If you’re wondering when we’re gonna talk about 4:6 because you’ve got a stack of 4 x 6 paper burning a hole in your printer, your days of wondering are over. A 4 x 6 print is a 2:3 aspect ratio. Doubling the units keeps the same shape and turns it into something more recognizable: 4:6, the shape of 4 x 6 prints.
4:5, 8:10, and 16:20 are all the same shape
A quick scan of your old math textbook would remind you that 8 x 10 can be reduced to its lowest terms by dividing both of those numbers by two. What you end up with is 4 x 5. 4 x 5 and 8 x 10 are indeed the same shape: they’re different sizes in terms of prints, but as far as shape goes, they’re the same.
To illustrate this, the following image has been segmented into both 4 x 5 and 8 x 10 units of measurement.
Cropping to adjust aspect ratio
If you need to change the aspect ratio of an image you've created to, say, a 4:5 aspect ratio, use an aspect ratio calculator like Ratio Buddy. In the boxes of the second row, type in the ratio (4, then 5), click the lock icon, then type in any pixel number for the height or width on the top row, and you'll see the other dimension you need. Play around with the numbers. Then, in PicMonkey, open up the crop tool, enter the pixel dimensions, and click Apply. BOOM you just earned a merit badge, hoss.