Fit an image or video inside a different frame without cropping or stretching. Get the scaled content dimensions, exact bars on every edge and active screen percentage.
ffmpeg -i input.mp4 -vf "scale=1920:1080:force_original_aspect_ratio=decrease:force_divisible_by=2:reset_sar=1,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:color=0x000000" -c:a copy output.mp4
The calculator proportionally scales the source until it fits completely inside the output frame. It then divides the unused pixels between opposite edges. A one-pixel difference is shown when an odd number of pixels cannot be split equally.
scale = min(frame width ÷ source width, frame height ÷ source height)unused width = frame width − scaled widthunused height = frame height − scaled heightThe active percentage compares the scaled picture area with the complete output frame. The remaining percentage is padding, not lost image content.
Letterboxing adds horizontal bars above and below the picture. It happens when the source is wider than the output frame—for example, a 1920×800 cinematic image inside a 1920×1080 frame.
In that example the image stays 1920×800, leaving 280 unused vertical pixels: 140 at the top and 140 at the bottom.
Pillarboxing adds vertical bars on the left and right. It happens when the source is narrower than the output frame. A 1440×1080 4:3 source inside a 1920×1080 16:9 frame leaves 480 horizontal pixels.
A centered fit places 240 pixels on each side and uses 75% of the output frame area.
Preserves the entire source and its proportions. Unused frame space becomes letterbox or pillarbox bars.
Fills the output frame without bars, but removes source edges. Measure the loss with the crop loss calculator.
Uses the whole frame without bars or cropping, but changes proportions and visibly distorts the content.
The generated filter first scales the video down to fit while preserving its aspect ratio, then pads it to the requested output dimensions and centers the active picture.
force_divisible_by=2 produces even scaled dimensions for common video encoders. As a result, FFmpeg bars can differ from the general pixel preview by one pixel in edge cases.
Method reference: FFmpeg scale filter and FFmpeg pad filter.
The visual calculation assumes square pixels, which is standard for most modern web images and video. Older or anamorphic sources can store a sample aspect ratio other than 1:1, so their displayed shape may not equal width divided by height.
The generated command resets the scaled output to square pixels. A separate pixel aspect ratio calculator will cover storage, sample and display ratios later.
The bars do not crop or stretch the source. Quality can still change if the source is scaled or the video is re-encoded, but padding itself does not remove visible source content.
An odd number of unused pixels cannot be divided into two equal whole-pixel bars. A centered result places the extra pixel on the bottom or right edge.
No. Black is conventional, but padding can use another color or a designed background. Choose a color above to update the preview and FFmpeg command.
The source scales proportionally to fill the frame with no bars. The result is reported as a perfect fit.
No. It only calculates geometry from numbers in your browser. The optional FFmpeg command can be run locally on your own file.