When do you need to resize an image?
Almost every platform has its own size rules. Passport and visa photo uploads, job applications and exam forms ask for exact dimensions. Social networks recommend particular sizes for profile pictures, banners and posts. Website themes look best when images match the layout, and email newsletters need small, light images. Resizing to the size you actually need also makes files much smaller.
This resizer runs in your browser, so photos are never uploaded. It keeps the proportions by default, so faces and products never look stretched, and it uses multi-step downscaling for a sharper result than a single resize.
How to use the image resizer
- Choose, drag or paste an image. Its current size is filled in.
- Resize by pixels: type a new width and the height follows automatically while keep aspect ratio is ticked. Untick it to set both sides freely.
- Or resize by percentage, for example 50% to halve both sides.
- Choose an output format and quality, check the preview and new file size, then download.
Keeping the aspect ratio
The aspect ratio is the relationship between width and height. A 1600 × 900 photo has a 16:9 ratio. To keep it while changing the width, the new height is calculated as:
New height = New width × Original height ÷ Original width
So resizing 1600 × 900 to a width of 800 gives a height of 450. If a form demands a different ratio, such as a square 600 × 600 photo, crop first with our image cropper so nothing gets squashed.
Common image sizes
| Use | Size (pixels) |
|---|---|
| Full HD wallpaper | 1920 × 1080 |
| Open Graph / link preview | 1200 × 630 |
| Instagram square post | 1080 × 1080 |
| Instagram story | 1080 × 1920 |
| YouTube thumbnail | 1280 × 720 |
Platform recommendations change from time to time, so check the current guidelines for important uploads.
More worked examples
Halving a photo: a 4000 × 3000 camera photo resized to 50% becomes 2000 × 1500 pixels, about a quarter of the original pixel count.
Common mistakes to avoid
- Unlocking the aspect ratio by accident. Faces and products look stretched; keep the ratio locked.
- Enlarging small images. Upscaling cannot add detail.
- Resizing when you need a different shape. Use the image cropper first, then resize.
Sources and methodology
The calculations on this page follow these published standards and references. The code is covered by automated tests against known values.