Quick answer: To resize without stretching, keep the aspect ratio: new height = new width × original height ÷ original width. A 4000 × 3000 photo resized to 1200 pixels wide becomes 1200 × 900. Making a picture smaller keeps it sharp, while enlarging it cannot add detail.
Profile pictures, thumbnails, blog headers and application forms all ask for a particular image size. This resizer changes the width and height of a picture to whatever you need, or scales it by a percentage, and it does all of it in your browser, so nothing is uploaded.
Load an image and its current size is filled in for you. Change the width and the height follows automatically when “keep proportions” is ticked. Quick buttons set common widths, and the preview and the resulting file size update as you go.
Tips for resizing
- Keep proportions. Leave this on so the picture is not stretched. The other side is calculated from the original shape: new height = new width × original height ÷ original width.
- Making it smaller is safe. Shrinking a picture keeps it sharp. Making it bigger cannot add detail that is not there, so enlarged pictures look soft.
- Common sizes. 1920 px wide suits a full-screen website image, 1080 px suits social media posts, and 256 to 512 px suits avatars and thumbnails.
- Save as. Use JPEG for photos and PNG for graphics with transparency. WebP is small and works in modern browsers.
The largest size the tool can produce is about 16 megapixels, for example 4096 × 4096, because that is the limit of the built-in image drawing in browsers on phones. Bigger pictures can still be loaded and made smaller.
A worked example
Example. A 4000 × 3000 photo resized to 1200 pixels wide with “keep proportions” on becomes 1200 × 900 (the height is worked out as 1200 × 3000 ÷ 4000). Choosing 50% gives 2000 × 1500 instead.
Sizes for common aspect ratios
| Aspect ratio | At 1920 px wide | At 1280 px wide | At 800 px wide |
|---|---|---|---|
| 4 : 3 | 1920 × 1440 | 1280 × 960 | 800 × 600 |
| 3 : 2 | 1920 × 1280 | 1280 × 853 | 800 × 533 |
| 16 : 9 | 1920 × 1080 | 1280 × 720 | 800 × 450 |
| 1 : 1 | 1920 × 1920 | 1280 × 1280 | 800 × 800 |
Heights are worked out with height = width × ratio. Phone photos are usually 4:3, cameras 3:2, video 16:9.
| Purpose | Common size |
|---|---|
| Link preview image (Open Graph) | 1200 × 630 px |
| Video thumbnail | 1280 × 720 px |
| Full HD screen | 1920 × 1080 px |
| Square profile picture | 400 × 400 px |
Common sizes. Check the current requirements of the site you upload to.
Common mistakes to avoid
- Turning off “keep proportions” by accident. The picture is then squashed or stretched, so crop instead if you need a different shape.
- Enlarging a small image. It looks blurry because the extra pixels are guesses, so start from the largest original you have.
- Resizing for print with screen sizes. Print needs more pixels per inch than a screen, so check the size your printer asks for.
Go deeper: read our guide How to Compress Images for Your Website.
Frequently asked questions
How do I resize an image without losing quality?
Make it smaller, not bigger, and keep the proportions. Reducing size keeps a picture sharp. Saving as PNG avoids extra compression loss, while JPEG at a high quality setting is almost as good and much smaller.
Is my image uploaded?
No. The picture is processed in your browser and is never sent to a server.
What does “keep proportions” do?
It keeps the same width to height ratio as the original, so the picture is not squashed or stretched. When you change the width, the height changes to match.
Can I resize to an exact size like 800 × 600?
Yes. Turn off “keep proportions”, then type both numbers. Note that if the shape is different from the original, the picture will be stretched. To keep the shape, crop it first.
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Sources and further reading
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