Guide · The math
How much you lose cropping 16:9 to 9:16
Cropping 16:9 to 9:16 keeps 31.6% of the pixels: a 1920×1080 frame keeps 608×1080. The strip is 0.5625 times the source height, and the output is upscaled to 1080×1920, so the result gains no detail.
The math, step by step
A 9:16 crop keeps the full height and narrows the width. The strip width therefore comes from the height, not the original width: height times 9 divided by 16.
| Step | Math | Result for 1920×1080 |
|---|---|---|
| Strip width | height × 9 ÷ 16 | 1080 × 0.5625 = 607.5 → 608 px |
| Strip area | 608 × 1080 | 656,100 px |
| Original area | 1920 × 1080 | 2,073,600 px |
| Share kept | 656,100 ÷ 2,073,600 | 31.64% |
| Upscale to output | 1080 ÷ 608 | 1.78× |
Resolution table
| Source | Strip | Output | Scale |
|---|---|---|---|
| 1280 × 720 | 405 × 720 | 1080 × 1920 | 2.67× (upscale) |
| 1920 × 1080 | 608 × 1080 | 1080 × 1920 | 1.78× (upscale) |
| 2560 × 1440 | 810 × 1440 | 1080 × 1920 | 1.33× (upscale) |
| 3840 × 2160 | 1215 × 2160 | 1080 × 1920 | 0.89× (downscale) |
| 4096 × 2160 | 1215 × 2160 | 1080 × 1920 | 0.89× (downscale) |
| 1440 × 1080 (4:3) | 608 × 1080 | 1080 × 1920 | 1.78× (upscale) |
The scale matters: below 1× you are downscaling, and downscaling keeps detail; above 1× you are upscaling, and upscaling invents no pixels. Only 4K crops without upscaling. A 720p file cropped to 9:16 is upscaled 2.67 times, and that shows on a modern phone.
How much you lose in other ratios
| Ratio | Strip | Kept |
|---|---|---|
| 9:16 (vertical) | 608 × 1080 | 31.6% of area |
| 4:5 (Instagram feed) | 864 × 1080 | 45.0% of area |
| 1:1 (square) | 1080 × 1080 | 56.3% of area |
| 16:9 (no crop) | 1920 × 1080 | 100% |
When to shoot vertical in the first place
If 80% of the views will happen vertical, shooting horizontal and cropping is doing the work twice. Shooting vertical keeps 1080 real pixels of width instead of 608 upscaled ones, and removes the framing decision afterwards. Cropping makes sense when the footage already exists: an interview, a talk, gameplay recorded horizontal.
- Interview or one-person talk → cropping works well.
- Wide landscape shot → cropping removes the reason for the shot.
- Gameplay with HUD in the corners → cropping eats the information; fill instead.
- Content published in both orientations → shoot 4K and crop two versions.
Why the output is always 1080×1920
It is the size TikTok, Reels and Shorts expect, and it is what keeps the platform from re-encoding the file. A larger output is heavier and does not look better on a phone; a smaller one gets rescaled with loss. For vertical, 1080 pixels wide is the practical standard.
Frequently asked questions
Exactly how much is lost cropping to 9:16?
68.4% of the image area. A 1920×1080 frame keeps 608×1080 pixels, which is 31.64% of the total. The number changes if the source is not 16:9: a 4:3 source keeps a larger share, because the height is the same and the source was already narrower.
Can the loss be avoided?
Only two ways: fill the space with a background (blurred or solid), which keeps the whole frame but adds bars, or shoot vertical from the start. Cropping and keeping the whole frame are incompatible by definition.
Why upscale from 608 to 1080?
Because platforms expect 1080×1920 and the native strip is only 608 pixels wide. Upscaling adds no detail; the file looks as good at phone size, not better. If you need real vertical resolution, shoot vertical.
Is 4K worth it for cropping?
Yes, if the destination is vertical: 3840×2160 gives a 1215×2160 strip, which downscales to 1080×1920 with no upscaling. It is the only common resolution that crops without losing sharpness. In exchange, decoding 4K in the browser takes longer.
What if the source is 4:3?
The math is the same because the height is kept: a 1440×1080 source yields 608×1080. The difference is that 4:3 was already narrower, so the share kept relative to the source goes up, even though the final strip is identical.