What is the difference between Image Size and Canvas Size?

Image Size scales the photo itself to a new number of pixels. Canvas Size changes the size of the page around the photo and leaves the photo at its current scale.

How do I resize an image without stretching it?

Leave Constrain proportions ticked in the Image Size dialog and change only the width or the height. The other number updates to keep the shape.

Will resizing overwrite my original?

Not unless you choose to. Save as Copy writes a new file beside the original.

Photo Editor Beginner 3 min read Updated Oct 23, 2026 Pluto Photos 2.5.2

How to Resize an Image (and Change the Canvas Size)

Short answer

Choose Image > Image Size, type a new width or height with Constrain proportions ticked, and click Apply. To add space around a photo instead of scaling it, use Image > Canvas Size.

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#1. Open the Image menu

With your photo open in the editor, open the Image menu. Image Size… changes how many pixels the photo has. Canvas Size… changes the size of the page the photo sits on. This tutorial uses a 1600 × 1200 photo.

The Image menu listing Image Size, Canvas Size, Rotate Left, Rotate Right, Flip Horizontal, Flip Vertical, Auto and Remove Background — Image Size and Canvas Size are at the top of the Image menu.

#2. Open Image Size and read the current size

The dialog shows the current Width and Height in pixels. Constrain proportions is ticked by default, which keeps the shape of the photo when you change either number.

The Image Size dialog showing a width of 1600 and a height of 1200 with Constrain proportions ticked — The Image Size dialog before any change: 1600 × 1200.

#3. Type the new width

Type the width you want and the height follows. Here, a width of 800 gives a height of 600. To set the two numbers separately, untick Constrain proportions. That will stretch the photo.

The Image Size dialog after entering a width of 800, with the height updated to 600 — A width of 800 gives a height of 600 with the proportions locked.

#4. Click Apply and save

Click Apply. The status bar at the bottom left now shows the new size. Save with Save as Copy (Ctrl+S) to keep your original at full size.

The editor after resizing the Tower Bridge photo to 800 by 600 pixels — The resized photo is 800 × 600 px.

#5. Or add space with Canvas Size

Choose Image > Canvas Size… to make the page bigger or smaller without scaling the photo. Set the new Width and Height, click a square in the Anchor grid to choose where the photo sits, and pick what fills the new space under Extend with: Transparent, White, Black or a custom color. Use it to add a border, or to turn a landscape photo into a square with room around it.

The Canvas Size dialog with width and height fields, a 3 by 3 anchor grid and an Extend with menu set to Transparent — Canvas Size, with the anchor grid and fill color.

#Tips

Making a photo smaller is safe. Making it larger isn't, because enlarging can't add detail that was never captured. A big increase looks soft.
If you only need a smaller file to share, use the Resize slider in the Export tab. It scales the saved copy and leaves the editor untouched.
If you need an exact shape, crop to a ratio first and then set the size.

#Questions

What is the difference between Image Size and Canvas Size?: Image Size scales the photo itself to a new number of pixels. Canvas Size changes the size of the page around the photo and leaves the photo at its current scale.
How do I resize an image without stretching it?: Leave Constrain proportions ticked in the Image Size dialog and change only the width or the height. The other number updates to keep the shape.
Will resizing overwrite my original?: Not unless you choose to. Save as Copy writes a new file beside the original.

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