How to Change Brush Size with Bracket Keys in Paint.NET

In Paint.NET, dynamically adjusting your brush size using keyboard shortcuts streamlines your digital drawing and photo editing workflow. Rather than manually clicking into the toolbar to type a value or adjust a slider, you can quickly increase or decrease the width of tools like the Paintbrush, Eraser, and Clone Stamp using the left and right square bracket keys ([ and ]). This guide explains how to use these shortcuts effectively and what to do if they are not responding.

Using the Bracket Keys to Resize Tools

  1. Select a Brush Tool: Open Paint.NET and select any tool that utilizes a brush width from the Tools window. This includes the Paintbrush, Eraser, Clone Stamp, Recolor tool, and Shapes tool.
  2. Decrease Brush Size: Press the left bracket key ([) on your keyboard. Each press decreases the brush width.
  3. Increase Brush Size: Press the right bracket key (]) on your keyboard. Each press increases the brush width.

You can press the keys repeatedly for incremental changes or hold down either bracket key to rapidly adjust the size up or down. The updated width displays in real time in the "Brush width" box located on the top toolbar.

Brush Size Increments

Paint.NET scales the adjustment increment relative to your current brush size:

  • At smaller sizes (under 10 px), the brackets change the size by 1 pixel at a time for fine detail work.
  • As the brush size becomes larger, the increment automatically increases to larger steps (such as 2, 3, or more pixels per press) to allow faster resizing across large canvases.

Troubleshooting

If pressing the bracket keys does not change the brush size, verify the following:

  • Canvas Focus: Click anywhere on the active image canvas. If focus is trapped inside a text field, a numeric entry box, or another window, keyboard shortcuts for tools will not register.
  • Compatible Tool Selection: Ensure you have selected a tool that supports a variable brush width. Tools like the Magic Wand, Move Selection, or Gradient tool do not use brush sizing.
  • Keyboard Layout: The shortcuts rely on the physical keys located to the right of the P key on standard QWERTY keyboards. If you use a non-US or international keyboard layout, ensure your system registers the specific square bracket characters.