Resize an image and calculate its aspect ratio
Image dimensions are the width and height in pixels. Aspect ratio is the relationship between those two numbers. Keeping that relationship fixed prevents a photo from looking stretched or squashed while you resize it.
Use the kwivaro image resizer to calculate dimensions, apply a common ratio, preview the result, and save it as WebP, JPEG, or PNG without uploading the source image.
Aspect ratio formulas
When you know the width, calculate height with this formula:
height = width × ratio height ÷ ratio widthFor a 16:9 image that is 1280 pixels wide:
1280 × 9 ÷ 16 = 720 pixels highWhen you know the height, reverse the calculation:
width = height × ratio width ÷ ratio heightCommon image ratios and dimensions
| Ratio | Example size | Typical use |
|---|---|---|
| 1:1 | 1080 × 1080 | Square posts, profile images and marketplace thumbnails |
| 4:3 | 1600 × 1200 | Presentations, classic screens and general photography |
| 3:2 | 1800 × 1200 | Camera photos and landscape prints |
| 16:9 | 1920 × 1080 | YouTube thumbnails, video frames and widescreen displays |
| 9:16 | 1080 × 1920 | Shorts, Reels, Stories and vertical video covers |
These are practical examples, not mandatory sizes. Any dimensions with the same ratio produce the same shape. A 1280 × 720 image and a 1920 × 1080 image are both 16:9.
Resize without distortion
- Choose an image and note its original width and height.
- Keep the aspect-ratio lock enabled when changing one dimension.
- Use a preset only when the target platform requires a different shape.
- If the target ratio differs, crop the edges instead of stretching the image.
- Preview faces, text, and logos before downloading the result.
To change the visible composition rather than stretch it, use the image aspect cropper.
Choose WebP, JPEG, or PNG
- WebP: a good default for smaller web images.
- JPEG: widely compatible and suited to photographs.
- PNG: useful for transparency, text-heavy graphics, and lossless output.
Enlarging an image changes its pixel dimensions but cannot recreate detail that the source did not contain. For the sharpest output, start with an original that is at least as large as the required result.
한국어 요약
가로세로 비율을 고정하면 이미지가 찌그러지지 않습니다. 너비를 알 때 높이는 ‘너비 × 비율의 세로값 ÷ 비율의 가로값’으로 계산합니다. 16:9 이미지의 너비가 1280px이면 높이는 720px입니다. 다른 모양으로 바꿀 때는 이미지를 늘리지 말고 필요한 영역을 잘라내는 것이 좋습니다.