How to Set Aspect Ratio in Photoshop, Premiere Pro, Canva and CapCut

Cropping an existing image to a ratio:

1. Select the Crop tool (C).
2. In the options bar at the top, open the ratio dropdown and either choose a preset (1:1, 4:5, 16:9, etc.) or type a custom ratio into the two fields (e.g. 4 and 3).
3. Drag the crop handles on the canvas — the crop box will now constrain itself to that ratio no matter how you resize it.
4. Press Enter to apply.

Setting up a new document at a specific ratio:

1. File → New.
2. Rather than typing width and height separately, decide your ratio first, then pick pixel dimensions that reduce to it — for example, for a 3:2 ratio you could use 3000 × 2000 or 1500 × 1000.
3. If you're not sure a pair of numbers actually reduces to the ratio you want, running the width and height through a ratio calculator first avoids guessing.

Common mistake: using Image → Image Size to change the canvas shape instead of Image → Canvas Size or the Crop tool. Image Size scales the entire image (which can distort it if "Constrain Proportions" is off), while Canvas Size and Crop actually change the shape by adding or removing space.

Setting a sequence's aspect ratio:

1. When creating a new sequence (File → New → Sequence), open the Settings tab.
2. Set the Frame Size width and height directly — this is where the sequence's ratio is defined. Common video ratios: 1920 × 1080 (16:9), 1080 × 1920 (9:16 for vertical), 1080 × 1350 (4:5).
3. If your source footage doesn't match the sequence ratio, Premiere will show it letterboxed or pillarboxed by default — you'll need to scale and reposition each clip (Effect Controls → Motion → Scale) to fill the frame, or intentionally keep the bars if that's the look you want.

Changing ratio after the fact (repurposing a 16:9 edit into 9:16):

1. Duplicate the sequence rather than editing the original.
2. Change the new sequence's Frame Size to the target ratio.
3. Go through each clip and reframe it — this usually means scaling up and repositioning so the subject stays centred in the new, narrower frame, since a straight ratio change alone will squeeze or crop content unpredictably.

Common mistake: manually typing in a width and height without checking they reduce to a clean ratio, which produces "almost 16:9" footage that displays with faint letterboxing on ratio-strict platforms.

That reframe is a crop, and it has a measurable cost rather than a matter of taste. The aspect ratio converter reports how much of the original frame a 9:16 cut keeps, and how much background the padded alternative would need, so you can decide before working through every clip by hand.

Canva is built around ratio-first design, which makes this the most direct of the four tools:

1. When starting a new design, use the search bar to type the ratio or platform name directly (e.g. "Instagram Post", "YouTube Thumbnail", "Presentation") — Canva has pre-built canvas sizes for most common platforms and ratios.
2. For a custom ratio, choose Custom size, then enter width and height in pixels. Canva doesn't reduce or simplify what you type, so if you want a clean 16:9, enter dimensions that already reduce to it (1920 × 1080 rather than an arbitrary pair).
3. To reshape an existing design, use Resize (available on paid plans) — this attempts to rearrange elements into the new canvas automatically, though manual adjustment is usually still needed for text and image placement.

Common mistake: resizing a design built for one ratio into a very different one (say, 16:9 into 9:16) and expecting Canva's auto-resize to produce a finished result. It's a starting point, not a final layout — background images especially tend to need manual repositioning after a big ratio change.

1. When starting a new project, CapCut prompts you to choose a canvas ratio immediately — 9:16, 1:1, 16:9 and a few others are offered as presets.
2. To change ratio mid-project, use the canvas or ratio setting in the export or project settings menu. Existing clips will be automatically scaled to the new frame — check each one, since CapCut's auto-fill can crop out parts of the frame you want to keep.
3. For vertical repurposing of horizontal footage, CapCut's background fill options (blur, colour, or a duplicated blurred layer) are a fast way to fill the empty space on either side of the subject without stretching it.

Whenever a tool lets you type a custom width and height, the two most common mistakes are the same regardless of software:

1. Typing numbers that don't actually reduce to the ratio you intended — 1900 × 1070 looks close to 16:9 but isn't exact, and the mismatch becomes visible once you view it full-screen or a platform re-crops it.
2. Stretching instead of cropping when converting between ratios, which distorts every subject in the frame rather than simply losing some content at the edges.

Checking the exact reduced ratio and a clean matching pixel size before you set up a canvas or sequence — rather than after you've already built the design around the wrong shape — is the fastest way to avoid redoing the work later. The aspect ratio calculator on this site does that reduction for any pair of numbers you type.

Two follow-ups cover what these tools do not. A correct shape on screen says nothing about whether the file has enough pixels behind it for its destination, which is the question the explainer on DPI, resolution and aspect ratio answers. And if the canvas you are setting up is destined for social output, the platform ratio guide lists the size each network expects, so the frame is right the first time rather than after a re-export.

• 16:9 calculator
• 9:16 calculator
• 4:5 calculator
• Social media ratios guide
• DPI vs resolution
• Monitor ratios compared

Want the numbers rather than the theory? The aspect ratio calculator reduces any width and height to its simplest ratio and shows the exact pixel size for a target shape.