Understanding Brush Sizes

Understanding brush sizes can sometimes be confusing. Brushes are available in a variety of sizes, and the numbering and sizing scales differ between manufacturers, making them difficult to compare. This article explains the numbering system that often appears on the handle of paintbrushes and what the measurements mean.

Artists’ brushes are usually given numbered sizes, although there is no exact standard for their physical dimensions. The number on the side of the brush refers to the thickness, length, or width of the brush hair. Rather than accurately represent these measurements, the numbering system is meant to order the size of the brushes.

Confusion can arise because this number and its corresponding dimensions vary between manufacturers. They also usually vary between the different ranges offered by a single manufacturer. A brush labelled with a “6” may look completely different than a “6” brush made by a different manufacturer, or even by the same manufacturer. This is why when buying brushes, it’s important to not just go by the brush size number.

This diagram shows the key dimensions of the brush.
Handle and Ferrule size tend to vary depending the style of brush, e.g. brushes for oil painting tend to have long handles whereas brushes for watercolour are typically shorter.

The system is fairly standardised, though sizes vary from one manufacturer to another. For example, the European system runs smaller than the English system, so a Size 10 brush from Winsor & Newton won’t have exactly the dimensions as a Size 10 from ​da Vinci. Sometimes a manufacturer might also add a measurement, where a 4/0 brush is approximately equivalent to 1/64 in or 0.4 mm.

Brushes from different brushmakers vary not only in hair size, but also in their shape, which can affect the overall size and feel of the brush. Some brushmakers will use more slender handles, whereas others might use a thicker design that prevents the brush from rolling off the table.

Two Size 10 brushes from the same company might also not be the same size – manufacturers usually use different fibres and handles between their own ranges, to help distinguish them or make student ranges more affordable. The ferrule, the part that holds the handle and hairs together and in shape, also varies in size. For example, mop brushes can have a ferrule made of plastic and wire, which means more variation between brands.

If you’re buying brushes from a catalogue or online, remember to consider this if you’re not familiar with a particular brand or range.

You may also notice that small brush sizes increase by increments of one (for example 1, 2, 3… etc.) When you reach size 10, larger brush sizes usually increase by increments of two (10, 12, 14.. etc.). Most manufacturers size brushes this way, usually for reasons of economy when producing brushes with expensive hair.

If you’re buying brushes online and it’s a brand you’re not familiar with, check to see if there’s an indication of the actual width of the brushes in inches or millimetres. Brush width is measured on the hair, just above the ferrule.

From smallest to largest, the sizes are:

20/0, 12/0, 10/0, 7/0, 6/0, 5/0, 4/0 (also written 0000), 000, 00, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 18, 20, 22, 24, 25, 26, 28, 30

Brushes as small as 30/0 are manufactured by some companies but are not a common size. Sizes 000 to 20 are most common.

Decorators’ brush sizes are given in millimetres or inches, which refers to the width of the bristles. Common sizes are:

10 mm, 20 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm.
​1⁄8 in,​1⁄4 in, ​3⁄8 in, ​1⁄2in, ​5⁄8 in, ​3⁄4 in, ​7⁄8 in, 1 in, ​11⁄4 in, ​11⁄2 in, 2 in, ​21⁄2 in, 3 in, ​31⁄2 in, 4 in

If you favour a particular range of brushes, you’ll eventually get used to their sizing and know instinctively which size you prefer. Pay close attention to the listed dimensions of any new brushes you would like to try for the first time, to ensure that you purchase the right size brush for your needs.

Further Reading

A Family Matter: Handcrafting Brushes

Choosing The Right Frame For Your Artwork

Making Handmade Watercolours

Brush Cleaning Tips for Painters

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