The quick answer: find the ratio, pick the shape, reshape the video
You filmed a landscape video and every app wants something else. Shorts want it tall, the feed wants it nearly square and YouTube wants it wide. The aspect ratio calculator turns any size into a ratio, or a ratio and one side into the missing side, and then hands you to the tool that reshapes the video.
- Find your ratio. Type the width and height. 1920 × 1080 is 16:9.
- Pick the shape for where it is going. The table further down lists the common ones.
- Reshape it. Use Resize for Social to fit the whole picture, or the video cropper to cut to the shape.
- Check the result, and for vertical video look at the safe zones before you post.
What a ratio is, and the ones you will meet
To get the tidy form, divide both sides by their greatest common divisor. 1920 and 1080 share a divisor of 120, which leaves 16:9. A 1080 × 1350 post divides by 270 and leaves 4:5, and a 4000 × 3000 photo divides by 1,000 and leaves 4:3. The decimal form (16 ÷ 9 = 1.78) is the easiest way to compare shapes that do not share round numbers.
| Ratio | Decimal | Common size | Where you meet it |
|---|---|---|---|
| 16:9 | 1.78 | 1920 × 1080, 3840 × 2160 | YouTube's player, TVs and most camera video |
| 9:16 | 0.56 | 1080 × 1920 | Shorts, Reels, TikTok and Stories |
| 4:5 | 0.80 | 1080 × 1350 | Instagram and Facebook feed posts |
| 1:1 | 1.00 | 1080 × 1080 | Square posts and profile pictures |
| 4:3 and 3:2 | 1.33 and 1.50 | 4000 × 3000 (4:3) | Photos from phones (4:3) and most interchangeable-lens cameras (3:2) |
| 21:9 | about 2.33 to 2.39 | 2560 × 1080, 3440 × 1440 | Ultrawide monitors |
| 2.39:1 | 2.39 | 2048 × 858 | Cinema scope, in 2K |
"21:9" is a label, not an exact shape: 2560 × 1080 is really 64:27 (2.37:1) and 3440 × 1440 is 43:18 (2.39:1). Some sizes do not simplify neatly at all. The old 1366 × 768 laptop screen is 683:384, within a tenth of a percent of 16:9, which is why the calculator tells you both.
Platform rules drift. At the time of writing, YouTube's standard player is 16:9 and adapts to other shapes, often with black bars, and a video only counts as a Short when it is square or vertical. Instagram accepts Reels from 1.91:1 to 9:16, X's developer docs list 1:3 to 3:1, LinkedIn 1:2.4 to 2.4:1 and Facebook 9:16 to 16:9, depending on where the video appears. The platform's own help page has the last word.
Width from height: resizing without stretching
Keep the ratio and you keep the shape. The formula is width = height × ratio width ÷ ratio height, and the other way round for a known width. At 4:5, a 1080-wide post is 1350 tall (1080 × 5 ÷ 4).
| Starting from a height of | Ratio | Width (exact) | Width to use |
|---|---|---|---|
| 1080 | 16:9 | 1920 | 1920 |
| 1080 | 4:5 | 864 | 864 |
| 1080 | 1:1 | 1080 | 1080 |
| 1080 | 9:16 | 607.5 | 608 |
| 1080 | 2.39:1 | 2581.2 | 2582 |
| 480 | 16:9 | 853.3 | 854 |
The last column is rounded to an even number. Most video stores color at half resolution in both directions, so H.264 and similar encoders expect even sizes and may refuse or pad odd ones. That is why 480p video is usually 854 × 480, and why the calculator has a Round to even numbers switch, on for video and off for images.
Crop, fit or stretch: what each one costs
Put a 1920 × 1080 video into a 1080 × 1920 vertical frame and every method pays a different price.
| Method | What you keep | What it costs | Use it when |
|---|---|---|---|
| Crop to fill | A full-height slice, 608 pixels wide, 32% of the width | Everything outside the slice, and the slice must be enlarged 1.78 times (1920 ÷ 1080) to fill the frame, so it looks softer | One subject, near the middle |
| Fit with a blurred or solid background | The whole picture | Screen space: the picture shrinks to 1080 × 608, which is about 32% of the frame, with 656 rows of fill above and below | Wide shots, two people, text near the edges |
| Fit with black bars | The whole picture | The same space, left plain | A film or clip that should look untouched |
| Stretch | Everything, distorted | The true shape: the picture is stretched about 3.2 times more vertically than horizontally | Never |
A bigger source helps a lot. A 4K frame (3840 × 2160) leaves a 9:16 slice about 1,215 pixels wide, enough to fill a 1080 × 1920 export with room to spare, while a 720p source (1280 × 720) leaves 405 pixels. The same arithmetic works in reverse: a vertical 1080 × 1920 clip fitted into a 16:9 frame fills only 32% of it.
Both tools do this for you. The video cropper locks the box to 16:9, 9:16, 1:1, 4:5 or 4:3 and can find and remove black bars. Resize for Social offers the fits and a crop-to-fill, with a live preview, and warns when a picture is being enlarged a lot. With blur or color, zooming to 120 to 140% makes the video bigger on a phone, as covered in vertical video for Shorts, Reels and TikTok.
4:5, 1:1 or 9:16: a decision table
At 1080 wide, 4:5 is 1350 tall and 1:1 is 1080, so 4:5 takes 25% more height in a phone feed (1350 ÷ 1080 = 1.25). That is why 4:5 takes more room than a square in a phone feed. Instagram's supported feed shapes have changed over time, so check its help page for the current range.
| Where it is going | Shape to export | How to get there |
|---|---|---|
| YouTube video | 16:9, 1920 × 1080 or 3840 × 2160 | Already right for most camera video; crop or fit anything else |
| Shorts, Reels, TikTok | 9:16, 1080 × 1920 | Blur, color or crop in Resize for Social, then check the safe zones |
| Instagram or Facebook feed | 4:5, 1080 × 1350 | The same tool, 4:5 shape |
| X, LinkedIn, or one file for many places | 1:1 or 16:9 | Square works nearly everywhere; X recommends 16:9 or square |
| A photo or thumbnail, not a video | The platform's own size | Image Resizer, which has the sizes built in, or crop a photo to an exact size |
| A file with black bars baked in | Crop the bars off first | Remove black bars in the video cropper |
To make several shapes from one long video at once, see turning a long video into Shorts.
What goes wrong
- Faces look wide or thin. The frame was forced to a new shape. Crop or fit instead, never stretch.
- Bars appear inside your picture. The source was letterboxed. Remove them in the cropper first, then reshape.
- The vertical version is soft. A small source was enlarged to fill the frame. Use a 4K source, or fit with a blurred background.
- An export fails or comes out a pixel off. Odd sizes. Keep the even-number switch on.
- Text sits under the buttons. Check the safe zones before posting.
Reshaped the file and it still looks worse online? Platforms compress what you give them. Why your video looks worse after uploading covers what helps.