Calculator
What the Image Downscaler does
Image Downscaler: shrinks by a percentage using high-quality resampling, so text and edges stay clean. Everything runs in your browser and the file is never uploaded.
The Image Downscaler works on a file you choose, without sending it anywhere. The work happens inside your browser tab, so there is no upload to wait for and no queue.
Most people who open the Image Downscaler 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.
If you want to check the arithmetic, the field table, the method and a worked example are further down.
What do the Image Downscaler fields mean?
The Image Downscaler uses 3 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 |
| Scale | choose from 75%, 50%, 25% or 10% | 50% |
| Export as | choose from PNG, JPEG or WebP | PNG |
How does the Image Downscaler 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 calculation.
Range checks come first, so the formula only ever sees values it can handle.
What a typical run looks like
You provide: Image file, Scale and Export as
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: a download link for the new file and a short note on what changed.
Timing comes down to your own hardware, and the practical size limit is how much memory the browser will hand the tab.
Downscaling sizes
Downscaling is the operation that actually saves bytes, and it usually saves more than any format change. Halving both dimensions removes three quarters of the pixels.
| Use | Size | Ratio |
|---|---|---|
| Full HD | 1920 × 1080 | desktop hero |
| Standard web | 1200 px wide | article body |
| Mobile | 800 px wide | phone display |
| Thumbnail | 400 px wide | grid or card |
| Icon | 150 px wide | list item |
Worth knowing
- Serving a 4000px image into a 400px slot wastes roughly 99% of the bytes downloaded.
- Match the target to the largest size the image is actually displayed at, then double it if you are supporting high-density screens.
- Downscaling is lossy and irreversible. Keep the original.
- Always set width and height attributes on the resulting <img>, so the browser can reserve space and avoid layout shift.
Platforms revise their published specifications from time to time. Where a ratio and a pixel size conflict, match the ratio — every platform downscales an oversized image, but none of them will fix a wrong shape except by cropping it.
How to use it
- Choose your file under Image file, or drag it onto the drop area.
- Pick a value for Scale: the options are 75%, 50%, 25% or 10%.
- Pick a value for Export as: the options are PNG, JPEG or WebP.
- Press Downscale.
- The panel reports 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.
- Large files are limited by your available memory, not by an upload quota.
Frequently asked questions
The form asks for Image file, Scale and Export as. Every box already holds a working value, letting you treat it as a what-if tool rather than a data-entry form.
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.
Full double precision is used throughout; only the displayed figure is shortened.