Aspect Ratios Explained: 1:1, 4:5, 3:2, 16:9 and 9:16

An aspect ratio describes the shape of an image: the relationship between its width and its height. It is written as two numbers separated by a colon — width first, then height. A 1:1 image is square; a 16:9 image is 16 units wide for every 9 units tall, no matter how many pixels it has.

Ratio vs. resolution

Ratio and resolution are often confused. Resolution is the number of pixels (for example 1920×1080). Ratio is the shape. 1920×1080, 1280×720 and 3840×2160 are all different resolutions with the same 16:9 ratio. That is why you can resize an image without changing its shape — and why changing the shape always requires cropping (or stretching, which you should avoid).

How to calculate an aspect ratio

Divide the width and height by their greatest common divisor. For 1080×1350, both numbers divide by 270, giving 4:5. If the numbers do not divide nicely, divide width by height for a decimal: 1200 ÷ 630 ≈ 1.9, often written 1.91:1.

To find a missing dimension, use: height = width × (ratio height ÷ ratio width). A 4:5 image that is 1080 px wide must be 1080 × 5 ÷ 4 = 1350 px tall.

The most common ratios

Ratio	Shape	Common uses	Example size
1:1	Square	Profile photos, product images, feed posts	1080×1080
4:5	Tall portrait	Instagram and Facebook feed posts	1080×1350
2:3 / 3:2	Classic photo	Camera photos, 6×4″ prints, Pinterest (2:3)	1500×1000
4:3	Classic screen	Many phone camera defaults, tablets, presentations	1600×1200
16:9	Widescreen	Video, YouTube thumbnails, slides, banners	1920×1080
9:16	Full-screen vertical	Stories, Reels, TikTok, Shorts, phone wallpapers	1080×1920
1.91:1	Wide landscape	Link previews on Facebook, LinkedIn and X	1200×630

Choosing a ratio for your image

• Know the destination. If a platform shows images as 4:5, any other shape will be cropped or shown with bars. Our social media size cheat sheet lists the right shape for each placement.
• Think about the subject. Tall subjects (people, buildings) suit portrait ratios; landscapes and groups suit wide ones.
• Printing? Match the print size: 6×4″ prints are 3:2, 10×8″ prints are 5:4. Otherwise the lab will crop the edges for you.

Changing the ratio without distortion

Never force an image into a new shape by typing new width and height values with the aspect ratio unlocked — people and objects will look stretched or squashed. Instead:

1. Open the image in the crop tool and select the ratio you need.
2. Move the crop box so the important part is inside, using the thirds grid as a guide.
3. Apply the crop, then resize to the exact pixel size.

If you cannot afford to lose anything from the edges, the alternative is to place the image on a larger background (letterboxing) in a design program.