Image Dimension Scaler
Scale image dimensions proportionally from one known size, keeping the aspect ratio locked automatically.
About Image Dimension Scaler
An image dimension scaler answers a question every content workflow hits: if I change one side of an image, what must the other side be to avoid distortion? Resizing images by guesswork produces stretched or squashed pictures, and doing the ratio math by hand for every variant is slow. This tool computes the matching dimension automatically, keeping the aspect ratio locked.
The aspect ratio is the original width divided by the height, and it must stay constant through any scale. Given a target width, the tool divides by the ratio to find the height, and given a target height, it multiplies by the ratio to find the width. Because the calculation is pure arithmetic, both upscaling and downscaling work identically, and the output always matches what an image editor would compute when the constrain proportions option is checked.
Web designers generating responsive image variants, such as hero, thumbnail, and card sizes from one original, use it to fill in width and height attributes accurately. Content managers preparing images for CMS uploads, and anyone building Open Graph or social media images to a required size, will avoid distorted results. Photographers and students learning about aspect ratios also use it to understand how cropping and scaling interact.
How to Use
- Enter the image's original width and height.
- Type a target width or height.
- Read the matching dimension, with the aspect ratio preserved.
Example
1200×800, target width 600 600×400
The ratio is 1200:800 = 1.5:1. At width 600 the height must be 400 to keep the image from distorting.
FAQ
Why does my image look stretched if I change only one dimension?
Because the aspect ratio breaks. This tool always computes both dimensions so scaling never distorts the image.
Can it scale both up and down?
Yes, it works in both directions, which is useful for producing responsive image variants from a single original.
How do I know the original dimensions?
Right-click an image and choose inspect, or open it in any image viewer or editor which shows dimensions in the status bar.
Do I need to include width and height attributes on images?
They're recommended, because the browser can reserve space while the image loads, preventing layout shift. Using this tool's output for those attributes keeps the dimensions truthful and distortion-free.
What is the difference between resizing and resampling?
Resizing changes the dimensions while typically resampling pixels to preserve quality. This tool only calculates the new dimensions; the actual pixel resampling happens in an image editor.