Cropping to an Aspect Ratio: How Much of Your Photo Survives

Every crop starts from a shape you did not choose: the one your camera recorded. Most phone cameras save photos at 4:3, a rectangle a third wider than it is tall, or 3:4 when you hold the phone upright. The iPhone camera, for example, lets you switch between 1:1, 4:3 and 16:9 before you take the picture, and the 4:3 option is the one that matches the sensor. Interchangeable-lens cameras usually work at 3:2, the shape of 35 mm film, which is why a classic 6 × 4 inch print fits them without trimming.

Picking another ratio on the camera rarely gives you a different picture; it usually gives you a smaller part of the same one. Canon's manual for the EOS M50 Mark II puts this plainly: JPEG files are recorded at the ratio you set, but RAW files are always saved at 3:2, with the chosen ratio stored only as a note. In other words, a 16:9 setting is a crop the camera makes for you. That is why it pays to think in terms of the native frame and what each target shape removes from it.

Orientation adds a second variable. The same 4:3 sensor gives a landscape 4:3 frame when the phone is held sideways and a portrait 3:4 frame when it is held upright, and the two behave very differently once a target shape is applied. A destination that wants a tall frame is easy to serve from an upright photo and expensive to serve from a sideways one, and the reverse is true for widescreen. Before you look at any percentages, check which way the photo was taken and which way the destination runs, because that single comparison predicts most of the loss.

The arithmetic is simple once you see that a ratio crop keeps one side of the photo whole and shortens the other. If the target is wider than the original, the full width survives and the height is cut. If the target is taller, the full height survives and the width is cut. The share kept is the smaller ratio divided by the larger one. A 4:3 photo is 1.33 times as wide as it is tall; 16:9 is 1.78 times. Divide 1.33 by 1.78 and you get 0.75, so a 16:9 crop keeps three quarters of the frame.

The same calculation works for every pair. A square, at 1.0, kept from a 4:3 photo is 1.0 divided by 1.33, again 75 percent, but this time the loss comes off the sides. A 3:2 crop from 4:3 keeps about 89 percent, because the two shapes are close. Going across orientations is where the numbers fall: a vertical 4:5 cut from a landscape 4:3 photo keeps 60 percent, and a 9:16 phone-screen frame keeps only 42 percent. The strip below shows the four results most people run into when they crop a landscape phone photo.

Widescreen is the most common target for a landscape photo: desktop wallpapers, slide backgrounds, video thumbnails and TV screens all use 16:9. From a 4:3 original the crop takes a quarter of the height, which in practice means an eighth from the top and an eighth from the bottom if the box stays centered. On a 4032 × 3024 phone photo that leaves 4032 × 2268 pixels, about 9.1 megapixels, still more than four times what a 1920 × 1080 screen shows.

What suffers is anything near the top or bottom edge. Landscapes usually lose sky and foreground, which is often an improvement. Groups and portraits are where trouble starts: people framed tightly from head to toe lose either the tops of their heads or their feet, and a tall building loses its roof. Moving the crop box helps, since you can take the whole quarter from the bottom if the important part is near the top. Starting from a 3:2 camera photo is kinder, because 16:9 then keeps about 84 percent and the strips are thinner.

Tall shapes are where the starting orientation decides everything. A phone photo taken upright is already 3:4, so a 4:5 portrait crop keeps about 94 percent of it and a 9:16 story frame keeps 75 percent, the same loss as widescreen from landscape, only taken off the sides. The same 4:5 crop from a photo taken sideways keeps 60 percent, and 9:16 keeps just 42 percent. Nearly three fifths of a landscape picture disappears when it becomes a full-screen vertical frame.

That is the arithmetic behind a common disappointment: a wide group photo or a landscape cut into a vertical frame turns into a close-up of whatever was in the middle. For a feed post the fix is to shoot upright when you know the destination is vertical. The guide on planning one Instagram photo for the feed, grid and stories shows where to place a subject so it survives every vertical crop. The iPhone's Photos app has a 9:16 crop preset alongside Square and 5:7, which is handy for checking the cost on the phone before you commit.

A square keeps the short side of the photo whole and trims the long side down to match. From either a 4:3 landscape or a 3:4 portrait, that means 75 percent survives; from a 3:2 camera photo, two thirds. Squares are still common for profile pictures, product listings and thumbnails, and they forgive one thing: the subject can sit in the middle without looking awkward, because a square has no long axis for the eye to travel along.

The catch is that many photos are not composed around the middle. The rule of thirds, which phone grids encourage, places a subject a third of the way in from one side, and a centered square crop of a 4:3 landscape removes an eighth of the width from each side, which can cut into a subject placed near the edge. Move the box toward the subject rather than accepting the center. For document photos, a square or near-square frame is often defined by the authority itself, and the guide on what a passport size photo means when a form gives no size covers those shapes.

Cropping is not the only way to change a ratio. Padding places the whole photo inside a frame of the new shape and fills the leftover space, usually with a plain color. Nothing is removed, but the photo appears smaller inside the frame, with bars on two sides. Stretching, the third option, forces the photo into the new shape and distorts everything in it, which is almost never what you want for a photo of people or objects.

Padding wins when every part of the image matters: a screenshot whose text runs to the edges, a document, a painting or a poster, a wide panorama that has to go into a vertical slot, or a group photo where nobody can be left out. It also wins when the shapes are far apart, since the 42 percent left by a 9:16 crop of a landscape is often less useful than the full photo with bars. Cropping wins when the photo has empty space to spare, such as sky, floor or background, and when the destination fills the whole screen, where bars look like a mistake.

Many destinations ask for a size in pixels rather than a ratio: 1920 × 1080 for a wallpaper or a slide, 1080 × 1350 for a portrait post, 600 × 600 for some application photos. A pixel size is a ratio plus a resolution, so the work splits into two steps. First choose the frame, using all the pixels of the original. Then scale that frame to the exact size. Doing it in that order means the crop is placed precisely and the final resize starts from the most detail available.

In practice you can crop the photo with the Aspect ratio locked to the target shape, drag the box over the part you want, and then scale it, or use a preset that does both at once. The 1920 × 1080 preset fills the Full HD frame with Crop to fill and lets you switch to Fit inside or Pad with color when nothing may be cut. For any other size, the Resize Image tool takes a width and height in pixels and the same choice under Fit. More image tools, from format conversion to compression, are listed on the image tools page.