Resize Image Online
Set a width, a height, or a percentage and get a resized copy in any format. Leave one dimension blank and it's calculated for you.
Why resize an image?
Exact or proportional
Enter just a width to keep the aspect ratio, both to fit inside a box, or untick 'Keep aspect ratio' to force exact dimensions. Leaving the height blank is the safest option — the correct height is worked out for you, so nothing is ever squashed or stretched.
Quality resampling
Images are downscaled with high-quality interpolation, so shrinking a photo stays sharp rather than jagged. Browsers do this in a single step, which is why a 4000 px photo reduced to 800 px still looks clean rather than pixelated.
Resize before you compress
File size scales with area, not width. Halving both dimensions removes 75% of the pixels, which usually saves more than any quality slider will. Resize first, then compress — doing it the other way round throws the work away.
Nothing is uploaded
The resize happens on your own device using the Canvas API. Your images are never sent anywhere, so screenshots of private dashboards, client work and photographs of documents are all safe to drop here.
How to resize an image
- Set the size — type a width and/or height in pixels, or click 25% / 50% / 75%.
- Upload — drop your image(s) — the size applies to each one.
- Download — pick PNG, JPG or WebP output and grab the result.
What we measured
We resized five JPEG photos (quality 95) to smaller widths and compared the file size with the original.
| Setting | Result |
|---|---|
| 75% of the width | 30% of the original size |
| 50% of the width | 16% of the original size |
| 25% of the width | 6% of the original size |
| 50% width, then compress to 70% | 12% of the original size |
Halving the width leaves a quarter of the pixels, which is why resizing saves more than turning the quality slider down. Full method and numbers: resize vs compress, measured.
Frequently asked questions
Can I enlarge an image?
Yes, but upscaling can't invent detail — a small image made larger will look softer. It works fine for modest increases of 20–50%; beyond about 2× the softness becomes obvious.
Does it resize multiple images at once?
Yes. The same size settings apply to every file you drop; each is resized independently, and you can download them individually or all together as a ZIP.
What size should I resize to?
For a full-width hero image, 1920–2400 px wide. For an image inside an article, 1200–1600 px. For a thumbnail or card, 400–600 px. Those figures already include a 2× allowance for high-DPI screens, so an image displayed at 600 px on the page should be exported at around 1200 px.
Will resizing reduce the file size?
Almost always, and usually by a lot. A 12-megapixel phone photo of about 4 MB typically drops to under 400 KB when resized to 1600 px wide, before any compression is applied at all.
Does it keep transparency?
Yes, if you export as PNG or WebP. Exporting to JPG flattens transparent areas onto a background colour, because JPG has no alpha channel.
Can I resize by percentage instead of pixels?
Yes — the 25%, 50% and 75% buttons scale each image relative to its own dimensions, which is useful when you're resizing a batch of images that aren't all the same size.
Is this tool free?
Yes — every tool on ConvertPicto is completely free, with no account, no watermark and no file limits. The site is supported by ads.
Are my images uploaded to a server?
No. ConvertPicto runs entirely inside your browser using the Canvas API. Your files are read locally, processed on your device and never sent anywhere — we don't even have a server that could receive them.
Does it work on my phone?
Yes. The site is fully responsive and works in any modern mobile browser (Chrome, Safari, Firefox, Edge). Processing large images is naturally slower on a phone than on a laptop.