Compare a centered crop that fills the destination with a fit that preserves the whole source and adds padding. The result describes ideal geometry. It does not inspect the image, locate a face or decide where the important subject should sit.
How the calculation works
Crop-to-fill uses the larger of target width/source width and target height/source height as its scale. Fit-with-padding uses the smaller. The tool derives the visible source rectangle or output padding from that scale, including centered offsets. Exact boundaries can be fractional.
Worked example
Filling 1080 × 1920 from 1920 × 1080 requires a 1.7778× scale and a visible source region of 607.5 × 1080 pixels. A centered crop starts 656.25 pixels from the left and retains about 31.64% of the source area. Fitting instead keeps the entire frame with padding above and below.
Before using the result
Both methods assume square pixels and uniform scaling. Rounded integer crop controls in an editor can differ slightly from the ideal result. The calculator does not predict image sharpness, stabilization margins or animated reframing. Inspect every shot, including titles and subtitles; centered framing is only a starting point.
Keep the source values with your project notes. A number calculated from an assumed bitrate or representative sample is only as useful as that assumption. Check a real file or measured export when a deadline, upload cap or storage purchase depends on the answer.