How to resize an image

First, work out what "size" you actually need

"Resize this image" can mean three different things, and doing the wrong one is the most common reason people end up going round in circles:

• Dimensions — the number of pixels wide and tall, like 4032 × 3024. This is what resizing changes.
• File size — how many kilobytes or megabytes the file takes up. Resizing reduces it as a side effect, but compression is the direct way to control it.
• Shape — square, 16:9, 4:5 and so on. You can't change the shape by resizing without stretching the picture; that's a job for cropping.

Converting print sizes to pixels: divide the size in centimetres by 2.54 and multiply by the dpi. A 10 × 15 cm print at 300 dpi needs about 1,181 × 1,772 pixels. The dpi number stored inside an image file on its own changes nothing about how sharp it is — only the pixel count does.

How to resize an image in your browser

This works on any computer or phone and handles a whole batch at once.

1. Open Image Resize and drop in your JPG or PNG images.
2. Choose Percentage (25%, 50% or 75% of each image's size) or Exact size (px).
3. For an exact size, fill in just the width (or just the height) to scale proportionally. Or fill in both and leave Fit within this size ticked, so each image shrinks to fit inside that box without being squashed.
4. Leave Don't enlarge on, so small images aren't blown up and made blurry.
5. Save. One image downloads directly; several come back as a .zip.

The resizing happens in your browser using its built-in canvas, so the images stay on your device. Each file keeps its original format, and PNG transparency is preserved.

How to resize an image on Windows

With the Photos app

1. Open the image in Photos.
2. Click the … (See more) menu and choose Resize image.
3. Choose pixels or percentage, keep the aspect ratio locked, and type the new width or height. You can also adjust the quality slider to trade file size against sharpness.
4. Click Save and give the copy a new name.

With Paint

1. Open the image in Paint and press Ctrl + W (or click Resize in the Image section of the toolbar).
2. Choose Pixels, make sure Maintain aspect ratio is ticked, and enter the new width.
3. Click OK, then File → Save as so you don't overwrite the original.

For regular bulk jobs, Microsoft's free PowerToys utility includes an Image Resizer that adds a Resize with Image Resizer option to File Explorer's right-click menu.

How to resize an image on a Mac

1. Open the image in Preview.
2. Choose Tools → Adjust Size.
3. Set the units to pixels, keep Scale proportionally and Resample image ticked, and enter the new width.
4. Click OK, then use File → Export to save a resized copy.

To do several at once, open them all in one Preview window, select every thumbnail in the sidebar, and use Adjust Size once. There's also a Finder shortcut: select images, right-click, choose Quick Actions → Convert Image, and pick an image size.

How to resize an image on your phone

iPhone: the Photos app can crop but doesn't have a simple "resize to pixels" option. The built-in Shortcuts app has a Resize Image action you can set up once and then run from the share sheet, and when you email large photos, Mail may offer to send them at a smaller size. For a one-off, a browser tool is quicker.

Android: it depends on the phone. Samsung's Gallery app has a Resize image option in the photo's menu (⋮); Google Photos doesn't have a straightforward one. Browser tools work on any Android phone.

Tips for a clean result

• Go down, not up. Shrinking an image looks fine. Enlarging one can't invent detail that was never captured, so it just looks soft or blocky.
• Keep the proportions locked. Typing both a width and height that don't match the original's shape stretches faces and squashes logos. Crop to the right shape first, then resize.
• Work on a copy. Once pixels are thrown away they're gone, so keep the original in case you need a bigger version later.
• Resize, then compress. If a file is still too heavy after resizing, run it through Compress Image. Resizing first means the compression has less to do.
• Pick the right format. Photos are usually best as JPG; screenshots, logos and anything with transparency as PNG. Our JPG vs PNG guide explains why.

As a rough starting point, around 1,200–2,000 pixels on the longest side is plenty for emailing photos or putting them in a document — far smaller than what a modern phone camera captures, with no visible loss on a screen. Always follow the exact numbers if a website or form gives you some.

Common questions