Change Video Aspect Ratio

Features

• Change to any aspect ratio — 16:9 (YouTube), 9:16 (TikTok / Reels / Shorts), 1:1 (Instagram), 4:3 (retro / TV), 21:9 (cinematic), or any custom ratio
• Three methods on one tool — stretch (fastest, distorts), crop (zoom in, no distortion), letterbox (black bars, no distortion, no crop)
• Live preview before processing — see exactly how the new ratio looks
• Runs in your browser via FFmpeg WebAssembly — your video never uploads to a server
• MP4, MOV, MKV, WebM all supported; audio preserved on every method
• Free with no watermark, no sign-up, no file size cap below plan limit

Quick Facts

• Cropping a 1920x1080 frame to 9:16 leaves 608x1080 - about 32% of the original width, so roughly two thirds of the picture is discarded. Source
• As decimals the common ratios are 16:9 = 1.78, 4:3 = 1.33, 1:1 = 1.00, 9:16 = 0.5625 and 21:9 = 2.33, which is why 16:9 to 4:3 is a mild change and 16:9 to 9:16 is a drastic one. Source
• All 3 methods force square pixels - a 1:1 pixel aspect ratio - on the output, so players report the new shape correctly instead of applying a stored ratio of their own.

Frequently Asked Questions

How do I change a video's aspect ratio online?

Drop your video into the aspect ratio changer, pick a target ratio (16:9 for YouTube, 9:16 for TikTok, 1:1 for Instagram square), choose method (stretch / crop / letterbox), click Process. Runs in your browser — no upload to a server.

What's the difference between stretch, crop, and letterbox?

Stretch distorts the video to fit the new ratio (fastest, no quality loss but people / faces look pinched). Crop zooms in and cuts off the edges (no distortion, but you lose some of the frame). Letterbox keeps the original frame and adds black bars on the sides or top/bottom (no distortion, no crop, just bars). Pick stretch for graphics-only content; crop for narrative video; letterbox for archives.

How do I convert horizontal video to vertical for TikTok / Reels?

Use 9:16 target. For a 16:9 source, the cleanest method is crop (zooms the center) — see our vertical conversion tool. Stretch will make people look very tall; letterbox will leave large black bars at top/bottom.

How do I convert 4:3 to 16:9 widescreen?

Use our dedicated 4:3 to 16:9 tool — pre-configured with the right stretch factor for old SD content.

Will changing aspect ratio reduce video quality?

Stretch and letterbox are near-lossless (only video container is re-encoded). Crop loses the cropped region but keeps the rest at full quality. No method adds compression noise — output uses high-quality H.264.

Is this aspect ratio changer free, no sign-up?

Yes — fully free, no watermark, no sign-up, no file size cap below your plan limit. Runs in your browser via FFmpeg WebAssembly so we have zero server costs to pass on.

How much of the frame do I lose cropping 16:9 to 9:16?

About two thirds of the width. A 1920x1080 frame cropped to 9:16 keeps 608x1080, so roughly 32% of the picture survives. Anything near the left or right edge is gone - which is why centered subjects crop well and wide shots do not.

Does changing the aspect ratio change the resolution too?

Yes - a new shape means new pixel dimensions. Crop reduces them, pad increases them, stretch rewrites them. Pixels stay square in all three cases, so the result reports its real size to every player.