Shoot wider than you deliver
If a project needs both a 16:9 master and a 9:16 cut, frame the shoot with the vertical crop in mind. Reframing in post from a 4K master is free; reshooting is not.
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Video aspect ratio calculator
Pick a ratio, enter the dimension you know, and get the other one. The delivery specs alongside are the ones each platform actually enforces.
Convert a file to this
Knowing the numbers is half of it. These do the conversion. Both re-encode video and copy the audio untouched. Dimensions are rounded to even numbers because H.264 rejects odd ones. Swap input.mp4 for your file.
Fit inside — pads with black
ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black" -c:a copy output-1920x1080.mp4Nothing is lost. Use when the whole frame matters, and accept the bars.
Fill the frame — crops the overflow
ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=increase,crop=1920:1080" -c:a copy output-1920x1080.mp4No bars, but the edges go. Check faces and captions survive the crop before you batch a folder.
Poster frame at 2 seconds
ffmpeg -ss 00:00:02 -i input.mp4 -frames:v 1 -vf "scale=1920:1080:force_original_aspect_ratio=increase,crop=1920:1080" poster.jpgA still for the video's poster attribute, so the slot is not black before playback starts.
NOTEWorth knowing
Mind the safe areas
Vertical platforms overlay their own interface across roughly the top 10% and bottom 15% of the frame. Captions and logos placed there get covered by a username and a like button.
4:5 beats 1:1 in the feed
On Instagram and Facebook, 4:5 occupies more vertical space than a square for the same scroll distance. Where a placement accepts both, 4:5 is the free upgrade.
16:9 for YouTube, websites and anything watched on a desktop. 9:16 for Reels, Shorts, TikTok and Stories. 4:5 for Instagram and Facebook feed, because it takes more vertical space than a square. If you only make one, make it 9:16. Cropping down to square or landscape from vertical loses less than the reverse.
ENDWhen planning is done
We make the film as well.
The tools handle the arithmetic. Directing, animating and cutting the thing is the part we are actually for.