How to Expand a Selection by Pixels in GIMP

Expanding an active selection outwards by a specific distance is a common task in GIMP used for creating borders, adjusting masks, and refining image cutouts. This guide provides the exact steps required to use GIMP's built-in "Grow" function to enlarge an existing selection boundary outward uniformly by a precise number of pixels.

Step-by-Step Procedure

1. Activate the Selection: Ensure you have an active selection on your canvas, indicated by the moving dashed line (often called "marching ants").
2. Open the Grow Tool: Navigate to the top menu bar, click on Select, and choose Grow... from the dropdown menu.
3. Set the Pixel Distance: In the dialog window that appears, find the input field labeled Grow selection by. Enter the exact number of pixels you wish to expand the selection outward.
4. Confirm the Measurement Unit: Ensure the dropdown menu next to the numerical value is set to px (pixels). GIMP supports various units like inches or millimeters, but pixels ensure exact screen measurement.
5. Apply the Change: Click the OK button.

The selection boundary will instantly shift outward in all directions by the specified pixel distance. If the selection reaches the edge of the image canvas, it will stop at the image boundary.