Image Resizer

Upload forms, online shops, social networks and print labs all want images at a particular size. This resizer scales one picture or a whole batch to an exact pixel size, a percentage or a print size in centimetres, millimetres or inches, and can fit, crop or pad to a fixed box. It runs in your browser — the images are never uploaded.

How to use this tool

1. Choose your images and the unit: pixels, percent or a print size.
2. Enter a width, a height or both. With one value the proportions are kept automatically.
3. If you entered both, pick how to fit the box: fit inside, fill and crop, pad with a colour, or stretch.
4. For print sizes set the dpi (300 is standard for photo prints); optionally change the format or set a maximum file size.
5. Download each resized image or the whole batch as a ZIP.

Formula

pixels = cm ÷ 2.54 × dpi = mm ÷ 25.4 × dpi = inches × dpi

With one side given, the other is original side × (new width ÷ original width). “Fit inside” uses the smaller of the two scale factors, “fill and crop” the larger. Downscaling is done in halving steps with high-quality smoothing to avoid jagged edges and moiré. For print units the dpi is also written into the file (JFIF density for JPG, the pHYs chunk for PNG) so layout programs open it at the right physical size.

Example

A 4000 × 3000 px photo resized to a width of 10 cm at 300 dpi becomes 10 ÷ 2.54 × 300 = 1181.1 → 1181 × 886 px (886 = 3000 × 1181 ÷ 4000, rounded), and prints exactly 10 cm wide. The same photo at 25% becomes 1000 × 750 px.