Resize GIMP Brush Size with Mouse Wheel

This guide explains how to configure GIMP to dynamically adjust your brush size using the mouse scroll wheel. By customizing GIMP’s built-in Input Controllers, you can bind brush radius expansion and reduction directly to your mouse wheel, significantly speeding up your digital painting and photo editing workflow.

Step 1: Open the Input Controllers Menu

  1. Launch GIMP.
  2. In the top menu, go to Edit and select Preferences (on macOS, go to GIMP > Preferences).
  3. In the Preferences window, locate the left sidebar and expand the Input Devices category.
  4. Click on Input Controllers.

Step 2: Enable the Main Mouse Wheel Controller

  1. Look at the Active Controllers column on the right.
  2. If Main Mouse Wheel is already listed under Active Controllers, double-click it.
  3. If it is listed under Additional Input Controllers, select Main Mouse Wheel and click the right-arrow button to move it to the Active Controllers column, then double-click it.

Step 3: Map the Scroll Actions to Brush Size

In the "Configure Input Controller" window, you will see a list of mouse wheel events. It is recommended to use a modifier key (like Alt or Shift) so you do not lose normal canvas scrolling functionality.

  1. Configure Scroll Up:
    • Scroll down the list and locate Scroll Up (Alt) (or simply Scroll Up if you prefer no modifier key).
    • Double-click the event to open the "Select Controller Event Action" dialog.
    • In the search bar at the top, type increase brush size.
    • Select Tools > Increase Brush Size (or Increase Brush Size by 1 for finer adjustments).
    • Click OK.
  2. Configure Scroll Down:
    • Locate Scroll Down (Alt) (or Scroll Down).
    • Double-click the event.
    • In the search bar, type decrease brush size.
    • Select Tools > Decrease Brush Size (or Decrease Brush Size by 1).
    • Click OK.

Step 4: Save and Test

  1. Click OK to close the Controller Configuration window.
  2. Click OK to close the main Preferences window.
  3. Select any brush tool (such as the Paintbrush, Pencil, or Eraser) and hold Alt while scrolling your mouse wheel over the canvas to dynamically resize the brush.