PRACTICAL HOW-TO

How to Choose Image Dimensions for a Website

The right image dimensions depend on the space the image will occupy, the largest screen size you need to support, and whether the image is decorative or contains important detail. There is no single pixel size that is correct for every website.

Before you start: Keep an untouched copy of the source file. Always follow the destination website or app’s exact upload requirements if they differ from this general guide.

Start with the displayed size

Find the actual width of the image slot in your page design. If a content column is about 800 CSS pixels wide, a 4000-pixel-wide photo may be unnecessarily large for that slot. A source image around 800–1600 pixels wide can be a reasonable starting point, depending on whether high-density displays and cropping are involved.

Account for high-density screens

A screen with a device-pixel ratio of 2 may use a 1600-pixel-wide source to render an image at 800 CSS pixels without looking soft. This does not mean every image needs to be double-sized: consider page performance, subject detail and whether the image is enlarged on the page.

Keep the aspect ratio unless you intend to crop

If the target box is 1200 × 600, it has a 2:1 aspect ratio. A 4:3 photo will not fit that box without either empty space, cropping or distortion. Prefer cropping intentionally over stretching, because stretching changes the shape of people and objects.

A practical workflow

First check the target slot, then resize a copy to a sensible pixel width, then export to an appropriate format. Use JPG or WebP for most photographs; use PNG when you need crisp lossless edges or transparency. Compare the output at the size it will actually appear on the page.

Example

Suppose a blog article displays a landscape photo in a 760-pixel-wide column. Start with a 1520-pixel-wide export if you want a 2× source for high-density screens. If the original is 5000 pixels wide, resizing it to 1520 pixels can reduce pixel data substantially before compression. The final file size will still depend on detail, format and quality settings.

Quick decision guide

File exceeds a KB/MB limit: compress the image; resize first if its dimensions are larger than needed.
Pixel dimensions are wrong: resize or crop, then recheck file size.
Format is rejected: convert to a format the destination explicitly supports.
Visual quality changed: compare the output with the original and try a less aggressive setting.

Related tools and explanations

Resize Image →Compress Image →Dimensions vs. file size →What image resolution means →

This guide explains general image-handling principles. Specific requirements vary by website, device, browser and export settings; verify the final file before using it.