Aspect Ratio Calculator
Enter a width and height to identify the aspect ratio, then calculate any matching size — no stretching, no black bars. Works for 16:9, 9:16, 4:3, 21:9, and custom ratios.
Aspect ratios for every platform
| Ratio | Typical size | Used for |
|---|---|---|
| 16:9 | 1920×1080 (1080p) | YouTube, TV, presentations |
| 9:16 | 1080×1920 (Reels/TikTok) | TikTok, Reels, Shorts |
| 4:3 | 1600×1200 | Classic screens, iPad |
| 1:1 | 1440×1440 | Square, Instagram feed |
| 21:9 | 3440×1440 | Ultrawide, cinematic |
| 3:2 | 2160×1440 | Photography, tablets |
How the aspect ratio calculator works
An aspect ratio is the proportional relationship between width and height. To find a matching size, the calculator solves new height = new width × original height ÷ original width — the cross-multiplication that keeps images and videos from stretching when you resize them.
It also simplifies your dimensions to the smallest whole-number ratio (1920×1080 → 16:9) and matches it against the standard ratios used by YouTube, TikTok, cinema, and photography.
Recording a video and want the size right from the start? The bitrate calculator pairs with this tool — pick the resolution here, then get the bitrate that keeps it sharp.
Aspect ratio FAQ
How do I calculate aspect ratio from width and height?
Divide both numbers by their greatest common divisor. 1920×1080 divides by 120 to give 16:9. This calculator does it instantly and also names the closest standard ratio.
What resolution is 16:9?
Any size where width ÷ height = 16 ÷ 9. The most common are 1280×720 (720p), 1920×1080 (1080p), 2560×1440 (1440p), and 3840×2160 (4K).
What aspect ratio is TikTok / Instagram Reels?
9:16 vertical, typically 1080×1920. YouTube Shorts uses the same. Square 1:1 (1080×1080) still works for Instagram feed posts.
How do I resize a video without stretching it?
Keep the ratio locked: multiply or divide both dimensions by the same factor. Enter your original size here, type the new width, and the calculator returns the height that avoids stretching or black bars.
What aspect ratio should an App Store preview video be?
Apple requires device-specific sizes, e.g. 886×1920 or 1080×1920 for iPhone portrait previews. A screen recorder with device-frame export like SmoothCapture handles those sizes automatically.
Perfect ratios, automatically
SmoothCapture exports your Mac screen recordings in the exact sizes platforms want — vertical 9:16 for Reels, 16:9 for YouTube, and App Store preview dimensions — with 3D device frames and smart zoom. Record and edit free; one-time purchase to export.