An aspect ratio is the shape of a picture: its width compared with its height, written as two numbers with a colon. A square is 1:1, a widescreen TV is 16:9 and a classic camera frame is 3:2. The ratio says nothing about size: a 1080 × 1080 image and a 3000 × 3000 image are both 1:1. Most confusion about photos that get "cut off" comes from shapes that do not match, which is why a phone photo loses its edges when it is printed as a 4 × 6, or why a post looks different in a feed than it did on your screen.
This guide shows how to work out the ratio of any image, which ratios are used where, and how to calculate exactly how much a print or a layout will trim.
How to find the ratio of any image
Divide the width and the height by their greatest common divisor, the largest number that divides both evenly. What is left is the ratio in lowest terms. You can also divide width by height to get a single decimal, which is easier to compare: anything above 1 is landscape, exactly 1 is square and below 1 is portrait.
| Pixels | Divide both by | Ratio | As a decimal |
|---|---|---|---|
| 1,080 × 1,350 | 270 | 4:5 | 0.800 |
| 1,920 × 1,080 | 120 | 16:9 | 1.778 |
| 4,032 × 3,024 | 1,008 | 4:3 | 1.333 |
| 6,000 × 4,000 | 2,000 | 3:2 | 1.500 |
| 1,080 × 1,920 | 120 | 9:16 | 0.563 |
| 1,200 × 630 | 30 | 40:21 | 1.905 |
The last row shows why some shapes are quoted by their decimal instead. 1200 × 630 reduces to the awkward 40:21, so people call it roughly 1.9:1. Paper has its own version of this. The ISO A series is designed around a long side √2 times the short one (about 1.41421), a shape no pair of whole numbers matches exactly, chosen because folding a sheet in half gives the same shape again. Real sheets are rounded to whole millimetres, though, so an A4 sheet at 210 × 297 mm is exactly 70:99, or 1.41429: a hair off the ideal and too close to see.
Portrait and landscape versions of a shape share one ratio, just flipped. 4:5 and 5:4 are the same rectangle turned on its side, and 9:16 is 16:9 stood upright. When you compare shapes, always put them in the same orientation first.
The ratios you will meet most
| Ratio | Decimal | Where it is used | Typical pixels |
|---|---|---|---|
| 1:1 | 1.00 | Square posts, profile pictures, product grids | 1080 × 1080 |
| 4:5 | 0.80 | Upright feed posts; the upright form of an 8 × 10 print | 1080 × 1350 |
| 4:3 | 1.33 | Phone camera default, tablets, older monitors and slides | 4032 × 3024 |
| 3:2 | 1.50 | 35 mm film (a 36 × 24 mm frame), many dedicated cameras, 4 × 6 prints | 6000 × 4000 |
| 7:5 | 1.40 | 5 × 7 inch prints and greeting cards | 2100 × 1500 |
| 16:9 | 1.78 | HD and 4K video, televisions, most laptop and desktop screens | 1920 × 1080, 3840 × 2160 |
| 9:16 | 0.56 | Vertical video, full-screen stories, phone screens held upright | 1080 × 1920 |
Two families dominate photography. 3:2 comes from 35 mm film, whose frame measures 36 × 24 mm, and most interchangeable-lens cameras kept it. 4:3 comes from early television and computer screens and is what most phone cameras record by default. Video and screens moved to 16:9, and phones held upright turned that into 9:16. Social feeds added 1:1 and 4:5 because a taller post fills more of an upright phone screen.
Why print sizes don't match your photos
Photo paper sizes were fixed long before digital cameras, and only one of the common ones matches a camera frame. A 4 × 6 inch print is 6 ÷ 4 = 1.5, exactly 3:2. A 5 × 7 is 1.4, which is 7:5. An 8 × 10 is 1.25, which is 5:4 (or 4:5 upright), and an 11 × 14 is about 1.27. When the photo and the paper disagree, the lab either trims the photo to fill the paper or leaves white bands.
To find the loss, compare the two decimals in the same orientation and divide the smaller by the larger. That is the share of one side that survives; the rest is cut. The table works it out for a 6,000 × 4,000 camera file and a 4,032 × 3,024 phone photo, filling the paper completely:
| Ratio | 3:2 camera photo | 4:3 phone photo | |
|---|---|---|---|
| 4 × 6 in | 1.500 | 6,000 × 4,000 kept, nothing cut | 4,032 × 2,688 kept, loses 11.1% of the height |
| 5 × 7 in | 1.400 | 5,600 × 4,000 kept, loses 6.7% of the width | 4,032 × 2,880 kept, loses 4.8% of the height |
| 8 × 10 in | 1.250 | 5,000 × 4,000 kept, loses 16.7% of the width | 3,780 × 3,024 kept, loses 6.3% of the width |
| 11 × 14 in | 1.273 | 5,091 × 4,000 kept, loses 15.1% of the width | 3,849 × 3,024 kept, loses 4.5% of the width |
| A4 (210 × 297 mm) | 1.414 | 5,657 × 4,000 kept, loses 5.7% of the width | 4,032 × 2,851 kept, loses 5.7% of the height |
Worked example: an 8 × 10 from a camera file
The print is 10 ÷ 8 = 1.25; the photo is 6,000 ÷ 4,000 = 1.5. Divide 1.25 by 1.5 and you get 0.833, so 5,000 of the 6,000 pixels across survive. The remaining 1,000 pixels are cut, 500 from each end if the lab centres it: 16.7% of the picture's width. Anyone standing near the edge of a group photo is at risk.
Worked example: a 4 × 6 from a phone photo
This time the paper (1.5) is more elongated than the photo (4,032 ÷ 3,024 = 1.333), so the lab keeps the full width and trims the height instead. 1.333 ÷ 1.5 = 0.889, leaving 2,688 of the 3,024 rows: 336 rows, or 11.1%, go, split between the top and bottom. A head placed close to the top of the frame can lose its hair. The same photo on a 5 × 7 loses only 4.8% of its height, which is why 5 × 7 often suits phone photos better.
Fitting instead of filling
If you ask for "fit" or "no crop", the whole picture is scaled to the paper's long side and the leftover space is left white. A 3:2 photo on 8 × 10 paper becomes 10 inches wide and 10 ÷ 1.5 = 6.67 inches tall, leaving a 0.67 inch band above and below. Some people like the look; others trim the white bands off with scissors, which gives a smaller print with nothing of the photo missing.
The same mismatch on screens
Screens do exactly what print labs do, only automatically. A layout that shows square thumbnails crops every landscape photo to its middle. A 16:9 video played full screen on an upright 9:16 phone either gets black bars above and below or, if it is made to fill the screen, keeps only (9 ÷ 16) ÷ (16 ÷ 9) = 31.6% of its width. That is why vertical video is shot vertically rather than cropped from widescreen footage afterwards.
When one photo has to serve several shapes, say a 16:9 banner, a 1:1 thumbnail and a 9:16 story, keep the subject inside the part that every centred crop keeps. For a 4,032 × 3,024 phone photo, the 9:16 crop is only 1,701 pixels wide and the 16:9 crop only 2,268 pixels tall, so the safe zone is the central 1,701 × 2,268 area: about 42.2% of the width and 75% of the height. Anything important outside it will be lost in at least one version.
Turning a ratio into pixel sizes
Once you know the shape you need, the other side follows from one multiplication: height = width ÷ ratio, or width = height × ratio. Round to a whole pixel.
- 4:5 at 1,080 pixels wide is 1,080 ÷ 0.8 = 1,350 pixels tall.
- 16:9 at 1,280 pixels wide is 1,280 ÷ 1.7778 = 720 pixels tall.
- 3:2 at 1,800 pixels wide is 1,800 ÷ 1.5 = 1,200 pixels tall.
- 9:16 at 720 pixels wide is 720 ÷ 0.5625 = 1,280 pixels tall.
Pixel counts decide sharpness, the ratio decides shape, and the two are independent. Our guide to choosing a pixel size covers how many pixels a print or a screen needs; this one is only about the shape.
A routine that avoids surprises
- Find out the shape of the destination: the print size, the video format or the layout slot.
- Turn it into a decimal and compare it with your photo's decimal to see which side will be trimmed and by how much.
- Crop the photo to that exact ratio yourself with the Crop Image tool, placing the frame where you want it, instead of accepting a centred cut.
- Check the pixel size left after cropping, then send the file. A lab or site that receives the right shape has nothing left to trim.
More guides
- JPEG, PNG, WebP or AVIF: Which Image Format to UseMeasured file sizes for JPEG, PNG and WebP at four quality settings on six test images, and plain rules for choosing a format for photos, screenshots and logos.
- How to Get an Image Under 200 KB, 500 KB or 1 MBMeasured width and quality settings that bring real photos under 200 KB, 500 KB and 1 MB, and why you should shrink the pixel size before lowering quality.