Image aspect ratio explained: 1:1, 4:5, 16:9 and more.

What aspect ratio means

An aspect ratio is written as two numbers separated by a colon, width first. 16:9 means that for every 16 units of width there are 9 units of height. The numbers are not pixels. A 1,920 × 1,080 image, a 1,280 × 720 image and a 640 × 360 image are all 16:9 because they all reduce to the same proportion.

To find a ratio, divide width by height, or divide both by their greatest common divisor. For 1,200 × 800, both numbers divide by 400, leaving 3:2. For 4,000 × 3,000, divide by 1,000 and you get 4:3. The decimal form helps with comparisons: 3:2 is 1.5, 4:3 is 1.33, 16:9 is 1.78 and 1:1 is exactly 1.

Common ratios and where they are used

Ratios swap when you rotate: 5:4 landscape is 4:5 portrait. Platform recommendations change over time, so check the current guidance for a given site. See Instagram image sizes and YouTube thumbnail size for examples.

What 1:1 means

1:1 means width and height are equal, a perfect square. A 500 × 500 image, a 2,000 × 2,000 image and a 1,080 × 1,080 image are all 1:1. Profile pictures are almost always requested as 1:1 because platforms then place them in a square or circle without distortion.

Most photos are not square, so you need to crop. Choose the square area around your subject; the step-by-step method is in how to crop a photo to a square.

What 5:4 (the "5 4 format") means

5:4 means the image is five units wide for every four units tall, a ratio of 1.25. It is a gently wide rectangle, close to square. In portrait orientation it flips to 4:5, which is the shape of an 8 × 10 inch print (8 ÷ 10 = 0.8, and 4 ÷ 5 = 0.8) and a popular tall shape for social posts such as 1,080 × 1,350 pixels.

If your photo is 4:3 (1.33) and you need 5:4 (1.25), you must trim a little from the long side. A 4,000 × 3,000 photo cropped to 5:4 keeps 3,750 × 3,000, losing 250 pixels of width. Going to 3:2 would instead mean losing height or width depending on the direction.

How to calculate a crop for a target ratio

Use the target ratio to work out the largest area you can keep.

1. Take your image size, for example 4,032 × 3,024 (4:3).
2. For a target of 16:9, keep the full width and set height = width × 9 ÷ 16 = 4,032 × 0.5625 = 2,268 pixels.
3. The crop is 4,032 × 2,268. You lose 756 pixels of height in total.
4. For a 1:1 target, use the shorter side: 3,024 × 3,024.

For a wider target the height shrinks; for a taller target the width shrinks. Never fix the shape by typing both width and height into a tool that stretches, because that distorts faces and circles.

How to change an image's shape without stretching

1. Open Crop image and add your photo. Rotate it first if it is on its side.
2. Drag the selection, or enter Left, Top, Width and Height in pixels. For example, from a 1,200 × 800 photo, Left 200, Top 0, Width 800, Height 800 gives a 1:1 square.
3. Export, then check the result for cut-off faces or text.
4. If you also need a particular size, open Resize image. It fits the image inside the width and height you enter, keeps the proportions and never stretches, so a 1,200 × 800 image resized to a 600-pixel maximum width becomes 600 × 400. It does not enlarge small images.

Do the crop first and the resize second. Resizing cannot change the ratio, and cropping first means the resize has all the pixels it needs. Both tools run in your browser, so the photo is not uploaded.

Common mistakes

• Stretching an image to force it into a box. Faces look wide or thin. Crop instead.
• Confusing ratio with size. 16:9 only tells you the shape, not the resolution.
• Putting important content at the edges when a platform may crop it. Leave a safe margin.
• Cropping first to the wrong ratio and then resizing a tiny result. Keep the original so you can retry.
• Forgetting orientation: 4:5 and 5:4 are different shapes, and so are 9:16 and 16:9.

Where to go next

If you are preparing photos for print, the sizes in photo print sizes and the pixel arithmetic in image DPI explained tell you how many pixels each shape needs. For websites, best image size for websites covers pixel widths. When you know the ratio you want, Crop image is the quickest way to get it.

Frequently asked questions

What does aspect ratio 1:1 mean?

It means width and height are equal, so the image is a perfect square. 500 by 500 and 1,080 by 1,080 pixels are both 1:1.

What is 5:4 aspect ratio?

5:4 means five units wide for every four tall, a ratio of 1.25. Turned upright it becomes 4:5, the shape of an 8 by 10 inch print.

How do I calculate aspect ratio?

Divide the width by the height, or divide both by their greatest common divisor. For example 1,200 by 800 reduces to 3:2.

Can I change aspect ratio without stretching the picture?

Yes, by cropping. Resizing keeps the proportions, so crop to the shape you want first and then resize if you need a particular pixel size.

Is 16:9 the same as 1920x1080?

1,920 by 1,080 is one size with a 16:9 ratio. 1,280 by 720 and 3,840 by 2,160 are also 16:9.