Aspect ratio and proportional resizing
Enter the original pixel width and height, then a target width. The calculator reduces the ratio and computes a height that preserves proportions. It calculates dimensions without uploading or modifying image files.
Formula and worked examples
New height = original height × new width ÷ original width. A 1920 × 1080 image is 16:9; at 1280 pixels wide, it becomes 1280 × 720. A portrait image at 1080 × 1920 is 9:16. A square at 1080 × 1080 is 1:1; a 1600 × 1200 photo is 4:3.
Resize, crop or stretch?
Proportional resizing preserves the image shape, cropping removes parts of the picture, and stretching distorts it. The output is a dimension calculation only, not an edited photo. If a result is fractional, use an appropriate whole-pixel height in your image editor. For physical rather than pixel conversions see our inches and centimetres converter.
More examples and FAQs
Aspect ratio describes the proportional relationship between image width and height. Formula: new height = original height × new width / original width.
For example, 1920 × 1080 pixels simplifies to 16:9. Scaling to a new width of 1280 pixels results in a 720-pixel height. This utility calculates dimensions only; it does not upload, crop or resize actual files.
Frequently asked questions
Is 1920 × 1080 equal to 16:9?
Yes. Dividing both dimensions by their greatest common divisor gives 16:9.
Does this tool resize a photo?
No. It only calculates the proportional dimensions; your image file remains untouched.
Resize proportionally by width or height
You can now calculate either dimension without uploading an image. Choose Find height from width to preserve proportions after setting the target width, or Find width from height for the opposite calculation. A 1920 × 1080 image targeted to 720 pixels high needs 1280 pixels of width. In both modes the original aspect ratio remains 16:9. The output is a dimension recommendation, not a resized downloadable image file.
Common aspect ratio presets and local image dimensions
Select 1:1, 4:3, 3:2, 16:9 or 9:16 to prefill compatible dimensions, then calculate a target width or height. The preview shows the selected proportion. You may also choose an image file on your device to read its pixel dimensions: the browser uses a temporary local object URL, without sending the file to our servers. The file picker accepts images up to 10 MB. This feature measures proportions only; it does not create or download a resized image.