Resize images online — exact pixels or ready-made presets

Pixels, aspect ratio and why resizing goes wrong

An image's aspect ratio is simply its width divided by its height. A 4000 × 3000 photo has a 4:3 ratio. If you force that photo into a 1080 × 1080 square without cropping, everything gets squashed — people look short and wide. That is the single most common resizing mistake.

There are three legitimate ways to change dimensions:

• Fit within a box — scale the image down until both sides fit inside your limits. The aspect ratio is preserved and nothing is distorted. This is what you want for websites and email.
• Exact size — force specific dimensions. Only safe when the target ratio matches the source, or when you accept the stretch.
• Percentage — multiply both dimensions by the same factor. Ratio preserved, useful for quick previews or thumbnails.

Resolution vs file size

Pixel dimensions and file size are related but different. A 4000 × 3000 photo of a clear blue sky compresses to a tiny file; the same dimensions of a dense forest can be ten times larger, because there is far more detail for the encoder to describe. If your goal is a smaller file rather than smaller dimensions, use the image compressor instead.

Print sizing

Print wants roughly 300 pixels per inch (PPI). An A4 sheet at 300 DPI is therefore 2480 × 3508 pixels. Screens are far more forgiving: a 1920 px wide image already fills most laptop displays.