Choose the right brush size for your project.

Decorators' brush sizes are given in millimeters (mm) or inches (in), which refers to the width of the head. Common sizes are:

• Metric: 10 mm, 20 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm.
• Customary: 1⁄8 in,1⁄4 in, 3⁄8 in, 1⁄2 in, 5⁄8 in, 3⁄4 in, 7⁄8 in, 1 in, 1+1⁄4 in, 1+1⁄2 in, 2 in, 2+1⁄2 in, 3 in, 3+1⁄2 in, 4 in.

If you're painting or varnishing woodwork, choose a small brush from more precise control, A 1.5-inch wide brush is ideal for most woodwork jobs. But, if you're painting trim that's wider than 3-inches, a little wider brush, up to 2.5-inches, would be a better choice. If you're painting walls you'll use a paintbrush primarily for cutting in. Pros sometimes use 3-or 4-inch wide brushes for this, but we think a 2.5-inch wide brush is ideal for most DIYers.

The only time you should consider a brush wider than 3 inches is if you're painting wide siding, fencing, paneling, or other wide, flat surfaces.