Aspect ratio calculator

Video Aspect Ratio Calculator — 9:16, 16:9, 4:5 Sizes

Aspect ratio mistakes are silent killers: a 16:9 video posted vertically gets letterboxed into a small strip, and a miscalculated crop ships with black bars. This calculator converts between ratios and pixel dimensions both ways, and includes the exact export sizes each platform expects.

Video aspect ratio calculator

Width (px)Height (px)

Simplified ratio: 9:16

Platform export sizes

TikTok / Reels / Shorts1080 × 1920 (9:16)
YouTube video1920 × 1080 (16:9)
Instagram feed portrait1080 × 1350 (4:5)
Instagram square1080 × 1080 (1:1)
X / Twitter landscape1280 × 720 (16:9)

Runs in your browser. Nothing is uploaded — your files never leave your device.

Quick answer

Pick a ratio above and enter one dimension to get the other instantly: 9:16 at 1080 wide is 1080 × 1920, the export size for TikTok, Reels, and Shorts. 16:9 at 1920 wide is 1920 × 1080 for YouTube. The calculator also simplifies any width × height into its exact ratio.

Which aspect ratio does each platform use?

Vertical 9:16 (1080 × 1920) is the format for TikTok, Instagram Reels, and YouTube Shorts, full-screen on a phone. Standard YouTube is 16:9 (1920 × 1080). Instagram feed posts perform best at 4:5 portrait (1080 × 1350), the tallest a feed post can be. Square 1:1 (1080 × 1080) still works everywhere as a safe middle.

Post the native ratio for each surface. Platforms letterbox or crop anything else, and vertical full-screen video measurably outperforms letterboxed landscape on every short-form feed.

Reframing between ratios without ruining the shot

Going from 16:9 to 9:16 means keeping roughly a third of the frame, so the crop has to follow the subject. Keep faces in the upper half, and leave headroom for platform UI: captions, buttons, and the description overlay eat into the bottom and right edges of a vertical frame.

If you shoot vertical on a phone, most of this disappears, and the edit is where ratios actually get enforced. Wavcut edits and exports true 9:16 on iPhone, with captions placed inside the safe area automatically, so the frame you preview is the frame every platform shows.

Frequently asked questions

What resolution is 9:16?

The standard export is 1080 × 1920 pixels, full HD vertical. Any width times 16/9 of that width keeps the ratio, e.g. 720 × 1280.

What aspect ratio do TikTok, Reels, and Shorts use?

All three are 9:16 vertical, 1080 × 1920. They accept other ratios but display them with dead space, which hurts watch time.

What is the best size for an Instagram feed post?

4:5 portrait at 1080 × 1350. It takes the most screen space a feed post is allowed; landscape posts get far less.

How do I find the aspect ratio of a video I already have?

Enter its width and height in the calculator; it reduces them to the simplest ratio, e.g. 1920 × 1080 → 16:9.

Should I export 4K for short-form?

Platforms compress aggressively, so 1080 × 1920 is the practical standard. A sharp, well-lit 1080p export beats a bitrate-starved 4K one after platform recompression.

How do I convert a landscape video to vertical without black bars?

Crop and reframe rather than letterbox: keep the subject centered and scale to fill 9:16. On iPhone, Wavcut edits natively in 9:16, so exports fill the frame with captions inside the safe zone.