Aspect Ratio Calculator

Enter the current width and height as positive whole numbers. The tool divides both by their greatest common divisor to express the same proportion with the smallest whole-number pair. The original pixel count is not changed by simplifying the notation.

Enter a new width to calculate a proportional height. The result rounds to the nearest whole pixel because a raster file cannot have a fractional row of pixels. The ratio can therefore differ very slightly after rounding, especially for small output dimensions.

For a small icon, examine the rounded pair before exporting. A mathematically proportional height can round below one pixel when the requested width is tiny compared with a very wide source. Such a result is not a usable raster size. Increase the target width or choose a different composition instead of trying to export a zero-height image.

The greatest common divisor of 1920 and 1080 is 120. Dividing both sides by 120 gives 16 and 9, so the simplified ratio is 16:9. Dividing width by height also gives approximately 1.7778; this decimal is another representation, not a new image size.

To keep the proportion at width 1280, multiply 1280 by 1080 / 1920. The answer is 720. The resulting 1280 × 720 image has the same 16:9 ratio, but fewer total pixels. Keeping a ratio does not keep the original amount of image detail.

A 1920 × 1080 image and a 3840 × 2160 image are both 16:9, but the second has four times as many pixels. The ratio describes shape. Resolution describes the dimensions of the pixel grid. File size depends on encoding and image content as well as that grid.

A square icon and a square photograph can both be 1:1 while using very different pixel dimensions and byte counts. Do not use an aspect-ratio result as proof that a file meets a platform’s minimum resolution or upload-size limit. Check those properties separately.

Width-to-height order matters. A landscape 16:9 image becomes a portrait 9:16 image when the axes exchange. Writing the larger number first regardless of orientation would erase an important property of the intended frame.

If source and destination have the same ratio, proportional resizing can fit the frame without cropping or borders. If they differ, you must choose a composition rule. Crop removes some source content, Pad preserves the full picture inside a larger canvas, and Stretch changes object proportions.

For example, a 4:3 photograph cannot fill a 16:9 frame while preserving all content and all proportions at once. A centered crop removes top and bottom content from the 4:3 source. Padding instead leaves unused space at the sides of a full-frame 16:9 canvas. Stretching fills the frame but changes shape.

The calculator does not decide which option is appropriate for the subject. A centered portrait, a text-heavy screenshot and a product photograph can require different choices. Inspect the actual resized or cropped result in an image tool before publishing it.

Use the pixel dimensions of the actual source file, not the width and height of a thumbnail on a web page. A thumbnail can be cropped, padded or displayed in a responsive box that does not match the underlying image. File properties or a trusted image editor can show the actual dimensions.

Do not mix units. If width is entered in pixels and height in centimeters, the simplified numbers have no useful geometric meaning. Both inputs need the same unit. This component labels its workflow in whole pixels, which also makes the rounding rule explicit.

Check the copied result after changing an input. The copy confirmation resets on edits so an older clipboard operation is not presented as a copy of the current calculation. The calculator does not store a history or update a file on your behalf.

Once you know the ratio and destination size, perform the actual image operation in a tool with explicit fit controls. Save a new file and verify its dimensions in the application where it will be used. A correct calculation is one step in the workflow, not a replacement for checking the exported asset.

Keep a small note of recurring image requirements: dimensions, ratio, format, background behavior and maximum bytes. That checklist is more useful than remembering only a phrase such as “wide image.” For a website or desktop widget, also check whether the display frame crops the supplied file.

Kepo offers Mac desktop widgets for small repeated workflows. The download button opens the app download page and does not transfer these numbers into an image widget automatically. Copy the dimensions yourself before moving to another application.