Calculator
What the Image Resizer does
Image Resizer: resize to an exact width and height (with or without keeping the aspect ratio), to a longest-side preset, or by a percentage, then export PNG/JPEG/WebP. Everything runs in your browser and the file is never uploaded.
The Image Resizer works on a file you choose, without sending it anywhere. Processing is local, so speed depends on your machine rather than someone else’s server load.
Most people who open the Image Resizer are people preparing images for the web. A smaller file that still looks right is usually only a few settings away.
The image is processed on your device and never uploaded, so personal photos stay personal.
The rest of this page documents each field, the method, and a worked example built from the values the image resizer loads by default.
What do the Image Resizer fields mean?
The Image Resizer uses 9 inputs. You do not have to fill everything in before seeing an answer; the starting values already produce one.
| Field | What to enter | Default |
|---|---|---|
| Image file | stays on your device | none |
| Resize by | choose from Width and height (pixels), Longest side (preset) or Percentage of original | Width and height (pixels) |
| Width | measured in px; accepts 1 to 10000 | 800 |
| Height | measured in px; accepts 1 to 10000 | 600 |
| Aspect ratio | choose from Keep ratio: fit inside width x height, Keep ratio: match width, auto height, Keep ratio: match height, auto width or Ignore ratio: stretch to exact size | Keep ratio: fit inside width x height |
| Longest side | choose from 64px, 128px, 256px, 512px, 1024px or 1536px | 512px |
| Scale | measured in %; accepts 1 to 400 | 50 |
| Output format | choose from PNG, JPEG or WebP | PNG |
| Quality % | accepts 10 to 100 | 90 |
How does the Image Resizer work?
Each output is derived from the inputs above in a single pass; there is no hidden state carried between runs, so the same inputs always give the same result.
The tool refuses to guess: if a value is missing or impossible, it says so.
What a typical run looks like
You provide: Image file, Resize by, Width, Height, Aspect ratio, Longest side, Scale, Output format and Quality %
What happens: the file is read into memory by your browser, processed locally, and offered back as a download. It is never uploaded.
You get back: the result as a file you can save, with a one-line summary beside it.
Nothing queues behind a server, so the wait is your device working, and the size limit is set by memory rather than by an upload cap.
Read next: JPEG, PNG, WebP or AVIF: Choosing an Image Format
How to use it
- Choose your file under Image file, or drag it onto the drop area.
- Pick a value for Resize by: the options are Width and height (pixels), Longest side (preset) or Percentage of original.
- Fill in Width in px (1 to 10000).
- Type Height in px (1 to 10000).
- Pick a value for Aspect ratio: the options are Keep ratio: fit inside width x height, Keep ratio: match width, auto height, Keep ratio: match height, auto width or Ignore ratio: stretch to exact size.
- Pick a value for Longest side: the options are 64px, 128px, 256px, 512px, 1024px or 1536px.
- Put Scale in % (1 to 400).
- Pick a value for Output format: the options are PNG, JPEG or WebP.
- Fill in Quality % (10 to 100).
- Press Resize.
- The results panel then shows Status.
- Copy Link puts the current inputs in the URL, so bookmarking it brings the same numbers back.
What this tool does not do
- EXIF metadata may be dropped during processing, which is usually desirable but is worth knowing.
- Re-encoding a lossy format such as JPEG always loses some detail, even at maximum quality.
- Results are informational: check anything consequential against a second source.
- Read the field labels once before trusting the answer; they specify the expected unit.
- Because everything runs locally, processing speed depends on your device rather than our servers.
Frequently asked questions
Enter Width in px, Height in px and Scale in %. Units are printed on the form itself. Match them and no manual conversion is needed.
Width accepts 1 to 10000 px. Values outside that range are rejected with a message naming the field, rather than producing something that looks valid but is not.
It is not uploaded. Everything happens on your device, so no copy of your file exists on any server.
No. There is no account, no usage cap and no trial period. The site is funded by advertising rather than by charging for the tools.
The logic is straightforward and testable; the worked example above uses the tool’s own defaults so you can verify it yourself.