Open the Canvas Size dialog and set your new dimensions
To change canvas size in Photoshop, go to the Image menu at the top and select Canvas Size. A dialog box will open showing your current canvas width and height in pixels (or whatever unit you have set). You can change these numbers to make your canvas larger or smaller. The dialog also shows an anchor point — a small grid that tells Photoshop where to position your existing image on the new canvas.
Before you change the numbers, decide where you want your image to sit on the new canvas. If you click the center square in the anchor grid, your image will stay centered when the canvas expands. If you click a corner, your image will stay pinned to that corner. This matters because it determines how much empty space (or how much cropping) happens on each side.
Key Takeaways
- Canvas size and image size are different — changing canvas size adds or removes space around your image without scaling the image itself.
- The anchor point in the Canvas Size dialog controls where your existing image sits on the new canvas.
- New canvas space fills with your background color by default, so set that first if you want a specific color.
- You can undo canvas changes immediately after, but once you flatten the image or save, the change is permanent.
Understand the difference between canvas size and image size
Canvas size and image size are not the same thing. Image size (also under the Image menu) scales your actual image up or down — it changes the pixels themselves. Canvas size adds or removes space around your image without touching the image. If you increase canvas size, you get blank space. If you decrease it, you crop the edges.
This distinction matters because scaling an image can blur it or make it look pixelated, while changing canvas size never affects image quality. If you need to add space for a border, background, or to fit a specific layout, canvas size is the right tool.
Set your background color before expanding the canvas
When you expand the canvas, the new space fills with your current background color. In Photoshop, the background color is shown as the bottom square in the toolbox on the left side of the screen. If you want the new canvas space to be white, black, or any other color, click that square and choose your color before you open the Canvas Size dialog.
If you expand the canvas and the new space is the wrong color, you can undo (Ctrl+Z on Windows, Cmd+Z on Mac) and change the background color, then try again. Once you flatten the image or merge layers, you cannot undo the color choice without starting over.
Use the anchor point to control where your image lands
The anchor grid in the Canvas Size dialog has nine squares — one in each corner, one in the middle of each edge, and one in the center. Whichever square you click becomes the anchor point. Your image will stay pinned to that spot when the canvas resizes.
For example, if you click the top-left corner square and then increase canvas width and height, your image stays in the top-left corner and blank space appears on the right and bottom. If you click the center square and increase the canvas equally, space appears evenly on all sides. This is useful when you want to add a border or frame around an image — center the image and expand outward.
Enter exact dimensions or use relative measurements
The Canvas Size dialog shows your current dimensions and lets you type new ones. You can enter absolute numbers (for example, 1200 pixels wide) or you can use the small arrows next to the width and height fields to increase or decrease by a set amount. Some versions of Photoshop also let you type relative values — for instance, typing "+200" adds 200 pixels to the current width.
If you are working with a specific layout or print size, knowing your target dimensions ahead of time makes this step faster. If you are experimenting, you can always undo and try different sizes.
Flatten the image if you want to merge all layers with the new canvas
When you change canvas size, the change applies to the entire document, but your layers stay separate. If you have multiple layers, they all sit on the new canvas independently. If you want to merge everything into a single layer that includes the new canvas space and background color, go to Image and select Flatten Image. This combines all layers and fills any transparent areas with the background color.
Flattening is permanent and cannot be undone after you save the file, so only do it when you are certain about your canvas size and ready to finalize the image.
Crop the canvas if you need to remove space instead of add it
Decreasing canvas size crops your image — it removes pixels from the edges. Set your new width and height to smaller numbers than your current canvas, and use the anchor point to choose which edges get cropped. For example, if you anchor to the center and shrink the canvas, Photoshop removes equal amounts from all sides. If you anchor to the top-left corner and shrink, the bottom and right edges get cropped.
You can see a preview of what will be cropped in the Canvas Size dialog before you confirm. If the preview shows you are about to lose important parts of your image, adjust the anchor point or cancel and try again.
Frequently Asked Questions
Can I undo a canvas size change?
Yes, immediately after you make the change. Press Ctrl+Z (Windows) or Cmd+Z (Mac) to undo. Once you close the file, flatten the image, or save, the change becomes permanent and cannot be undone through the undo history.
What happens to layers when I change canvas size?
Layers stay separate and keep their original size. The canvas expands or shrinks around them. If a layer is smaller than the new canvas, you will see transparent space (shown as a checkerboard pattern) or the background color. Layers do not automatically scale to fill the new canvas.
Can I change canvas size to a specific aspect ratio?
The Canvas Size dialog shows width and height separately, so you enter numbers that create any ratio you want. If you need a 16:9 ratio, for example, you could set width to 1600 and height to 900. Some versions have a chain link icon that locks the ratio, but you can click it to unlock and set width and height independently.
Does changing canvas size affect image resolution or DPI?
No. Canvas size changes only the dimensions in pixels (or inches, centimeters, etc.). Resolution and DPI stay the same. If you need to change DPI for print, use Image > Image Size and adjust the resolution there.
What if I want to add a border around my image?
Increase canvas size, set your background color to the border color you want, and anchor your image to the center. The new canvas space becomes your border. Adjust the width and height equally to create an even border on all sides.