What an aspect ratio describes
Aspect ratio describes shape, not resolution. 1080 × 1920 and 720 × 1280 are both 9:16 because their width-to-height proportions are the same.
Common shapes
Square 1:1 works naturally in grids. Portrait 4:5 uses more vertical feed space. Landscape 16:9 is common for conventional video. Vertical 9:16 fills most modern phone screens.
- 1:1 — square
- 4:5 — feed portrait
- 16:9 — landscape video
- 9:16 — vertical video
Use the calculator
ContentDown's Aspect Ratio Calculator reduces dimensions to their simplest ratio and provides equivalent sizes. It runs in your browser and does not upload an image.
Work through a crop
Suppose your image is 1920 × 1080 (16:9), but you need a 1:1 square. A centered square crop keeps 1080 × 1080 pixels and removes 420 pixels from each side. That may cut off subjects near the edges.
For a 4:5 crop at the same original height, the width would be 864 pixels, requiring a much narrower selection. Preview the framing before exporting rather than relying on the ratio label alone.
Equivalent dimensions are not equivalent quality
1080 × 1920, 720 × 1280 and 540 × 960 all share a 9:16 ratio. Their pixel counts differ substantially, however. Use the calculator to check shape, then inspect dimensions to decide whether the source contains enough detail for your intended output.