What You Will Learn

  • How to convert horizontal video (16:9) to vertical video (9:16)
  • How to extract a vertical video with a center crop (crop)
  • How to add black bars (pad) or a colored background
  • How to convert to vertical video with a blurred background
  • Recommended resolution settings for Instagram Reels and TikTok

Tested version: Verified with FFmpeg 6.1
Target OS: Windows / macOS / Linux

Tested with: FFmpeg 6.1 (verified against real FFmpeg)

Vertical Video Format Basics

ItemValue
Aspect ratio9:16
Resolution (standard)1080×1920 px
Resolution (minimum)540×960 px
Frame rate24–60 fps

Method 1: Center Crop (crop)

Cut out the center of a horizontal video at vertical-video dimensions. This works best when the subject is centered.

1920×1080 → 1080×1920 Center Crop

First scale the height up to 1920, then center-crop a width of 1080 from it:

ffmpeg -i input.mp4 -vf "scale=-1:1920,crop=1080:1920:(iw-1080)/2:0" output_vertical.mp4

Center-Crop a 9:16 Region from a Horizontal Video (No Scaling)

To cut a center 1080×1080 region out of a 1920×1080 video and make it vertical:

ffmpeg -i input.mp4 -vf "crop=1080:1080:(iw-1080)/2:(ih-1080)/2,scale=1080:1920:force_original_aspect_ratio=decrease,pad=1080:1920:(1080-iw)/2:(1920-ih)/2" output_vertical.mp4

Method 2: Black-Bar Padding (pad)

Shrink the entire video and add black bars on the top and bottom. Everything stays visible, but the black bars are conspicuous.

Fit a Horizontal Video into the Vertical Format with Black Bars

ffmpeg -i input.mp4 -vf "scale=1080:-2,pad=1080:1920:0:(1920-ih)/2:black" output_padded.mp4

Pad with a Colored Background

ffmpeg -i input.mp4 -vf "scale=1080:-2,pad=1080:1920:0:(1920-ih)/2:color=0x1a1a2e" output_padded_color.mp4

Use a blurred copy of the original video as the background, then overlay the original on top. There are no black bars, and the result looks visually natural.

ffmpeg -i input.mp4 -filter_complex "[0:v]scale=1080:1920:force_original_aspect_ratio=increase,crop=1080:1920,boxblur=20:3[bg];[0:v]scale=1080:-2[fg];[bg][fg]overlay=(W-w)/2:(H-h)/2[out]" -map "[out]" -c:v libx264 -b:v 8M -pix_fmt yuv420p -c:a copy output_blur_bg.mp4

The processing flow of this method:

  1. [bg]: Stretch the original video to 1080×1920 (ignoring the aspect ratio) and create the blurred background
  2. [fg]: Shrink the original video to a width of 1080 (preserving the aspect ratio)
  3. overlay: Composite it centered on top of the blurred background

Method 4: Crop at a Specific Position

When the subject is not centered, adjust the crop position.

Crop with the Left Side Prioritized (x=0)

ffmpeg -i input.mp4 -vf "scale=-1:1920,crop=1080:1920:0:0" output_left.mp4

Crop with the Right Side Prioritized

ffmpeg -i input.mp4 -vf "scale=-1:1920,crop=1080:1920:iw-1080:0" output_right.mp4

Crop at an Arbitrary x Coordinate

ffmpeg -i input.mp4 -vf "scale=-1:1920,crop=1080:1920:300:0" output_custom.mp4

Verifying the Aspect Ratio Precisely

ffmpeg -i input.mp4 -vf "crop=iw:ih*9/16:(iw-iw)/2:(ih-ih*9/16)/2" output.mp4

Keeping the Audio

You can preserve the audio in any of these commands by adding -c:a copy or -c:a aac -b:a 256k:

ffmpeg -i input.mp4 -vf "scale=-1:1920,crop=1080:1920:(iw-1080)/2:0" -c:v libx264 -b:v 8M -pix_fmt yuv420p -c:a aac -b:a 256k output_vertical.mp4

Basic Syntax of the crop Filter

crop=w:h:x:y
ParameterDescription
wWidth to crop
hHeight to crop
xCrop start position (from the left)
yCrop start position (from the top)

You can use variables such as iw (original width) and ih (original height).

Tested with: ffmpeg 6.1 / Ubuntu 24.04 (検証スクリプトで実行確認)
Primary sources: ffmpeg.org/ffmpeg-filters.html#crop / ffmpeg.org/ffmpeg-filters.html#pad

FAQ

1080×1920 (9:16) is the safest choice. Because TikTok re-encodes on its side, a bitrate of 5–8 Mbps is plenty.

Does converting horizontal video to vertical reduce quality?

If you are going in the direction of lower resolution (cropping), the degradation is essentially negligible. Conversely, the method of adding black bars on the top and bottom to reach 9:16 is not recommended — it worsens the viewing experience.

My vertical video shot on an iPhone plays sideways

The iPhone embeds “rotation metadata” when recording. Some players don’t read this and play the video sideways. The reliable approach is to physically rotate it on save with ffmpeg -i in.mov -metadata:s:v rotate=0 -vf transpose=1 out.mp4.

Should I create separate files for YouTube Shorts and TikTok?

In general, the same file is fine. Both platforms recommend 1080×1920; only the maximum length differs (Shorts up to 3 minutes (raised from 60s in late 2024) / TikTok 10 minutes). Choose based on the length of the video.

Which should I upload to first, Reels or Shorts?

Because platforms have algorithms that judge who the “original poster” is, we recommend uploading to your main platform first and posting to the others afterward.