How to use the calculator
- Resize keeping proportions: set the ratio (or click a preset like 16:9), then type the new width. The height updates as you type, and the other way around.
- Find the ratio of a size: uncheck "Lock the ratio" and type a width and height. The ratio box shows it simplified: 1920×1080 becomes 16:9, 1080×1350 becomes 4:5.
- Start from a known format: the size presets fill in both sides and the ratio, for example an Instagram portrait post (1080×1350) or an iPhone 6.9" App Store screenshot (1320×2868).
The table under the result lists common widths with the matching height for the current ratio, and marks the ones that do not come out to a whole pixel, so you can pick a size that scales cleanly.
The aspect ratio formula
An aspect ratio is width divided by height, written as two whole numbers. To get it from a resolution, divide both sides by their greatest common divisor: 1920 and 1080 share 120, so 1920×1080 is 16:9. To get a missing side, cross-multiply:
- new height = new width × ratio height ÷ ratio width. 1280 × 9 ÷ 16 = 720.
- new width = new height × ratio width ÷ ratio height. 1350 × 4 ÷ 5 = 1080.
Some real resolutions do not simplify to anything pretty. 1366×768, the classic cheap laptop screen, is exactly 683:384. In those cases the calculator also shows the decimal value (1.78:1) and the closest named ratio, which is what people actually mean when they call it "16:9".
Common aspect ratios and where they are used
| Ratio | Decimal | Typical use |
|---|---|---|
| 16:9 | 1.78 | HD and 4K video, YouTube, most monitors and TVs, slides |
| 16:10 | 1.6 | MacBook screens, many laptop displays |
| 4:3 | 1.33 | iPad, older monitors, many phone camera photos |
| 3:2 | 1.5 | DSLR and mirrorless photos, Surface screens |
| 1:1 | 1 | Profile pictures, square social posts, app icons |
| 4:5 | 0.8 | Instagram portrait posts (1080×1350) |
| 9:16 | 0.56 | Stories, Reels, TikTok, YouTube Shorts (1080×1920) |
| 21:9 | 2.33 | Ultrawide monitors, cinematic video |
| 1.91:1 | 1.91 | Link previews on Facebook, LinkedIn and X (1200×630) |
App Store screenshot sizes
Apple only requires the largest size per device family and scales it down for the rest. As of 2026 that is 1320×2868 or 1290×2796 for the 6.9" iPhone class, 1284×2778 or 1242×2688 for 6.5" iPhones, 2064×2752 or 2048×2732 for 13" iPads, and 2880×1800 (16:10) for Mac. If your screenshot does not match, App Store Connect rejects it, so check the exact pixels with the calculator before you export.
Screenshots that need a specific shape
A raw Mac screenshot is rarely the shape a social network wants. Instead of cropping it, put it on a background at the right ratio: the free screenshot beautifier has 16:9, 4:3, 1:1 and 9:16 output presets and runs entirely in your browser.