Brush Size Calculator — Real Brush to Pixel Size

Measure your real brush stroke width in millimetres. Enter your canvas dimensions (real and pixel). The calculator converts the brush width to an equivalent pixel size that produces the same proportional stroke on your digital canvas.

A 10 px brush on a 1000 px canvas covers 1% of the width. The same 10 px brush on a 5000 px canvas covers only 0.2%. The physical size equivalent changes with resolution — this calculator helps you find the right pixel size.

For A4 print at 300 DPI, work at 3508 x 2480 px. For larger prints, scale up. The canvas should match your intended output to ensure brush strokes have the right weight and texture when printed.

Most apps measure brush size in pixels as the diameter of the brush tip. However, brush opacity, flow and texture settings also affect the apparent stroke width. This calculator gives the geometric pixel diameter.

With pressure sensitivity enabled, the maximum brush size is what you set. Light pressure produces a thinner stroke. Set your brush size to match the maximum stroke width you want for that tool.