Ask a room of portrait painters which brush they would keep if they could only have one, and a large share will say a filbert. Its flat body lays down broad color like a flat brush, while its rounded tip softens edges and turns into petals, leaves and the curve of a cheek. The hard part is the numbering. A size 6 filbert from one brand can be noticeably wider than a size 6 from another, so a filbert brush size chart is most useful as a translation tool: it connects the number on the handle to the width you will actually see on the canvas.
Quick answer: Filbert brushes are commonly numbered from about 0 to 24. Approximate widths: sizes 0 to 2 are roughly 1/16 to 1/8 inch (2 to 3 mm), sizes 4 to 6 roughly 1/4 to 5/16 inch (6 to 8 mm), sizes 8 to 10 roughly 3/8 to 1/2 inch (10 to 12 mm), sizes 12 to 16 roughly 1/2 to 3/4 inch (13 to 19 mm), and sizes 20 to 24 roughly 7/8 to 1 inch or more. Sizes vary by brand, so check the listed width. A small (2 to 4), medium (6 to 8) and large (10 to 12) filbert cover most work on canvases up to about 16 by 20 inches.
What Makes a Filbert a Filbert
A filbert has a flattened metal ferrule like a flat brush, but its bristles are shaped into a rounded or oval tip. That combination gives it three different mark-making edges in one brush:
- The flat face covers areas with broad, even strokes.
- The rounded tip produces soft, tapered marks and blends edges without hard corners.
- The thin side edge makes fairly fine lines when turned on its side.
The name comes from the filbert nut (hazelnut), whose oval shape the brush resembles. Variants include long filberts with extended bristles for more spring, short “bright” style filberts with stiffer control, and filbert grainers or combs with split bristles for texture.
Filbert Brush Size Chart
The table below gives typical approximate widths. Real brushes vary by manufacturer, series and hair type, so treat these as ranges rather than exact specifications.
| Size number | Approximate width (inches) | Approximate width (mm) | Size group |
|---|---|---|---|
| 0 | About 1/16 | About 2 | Extra small |
| 2 | About 1/8 | About 3 to 4 | Small |
| 4 | About 1/4 | About 5 to 6 | Small |
| 6 | About 5/16 | About 7 to 8 | Medium |
| 8 | About 3/8 | About 9 to 10 | Medium |
| 10 | About 7/16 to 1/2 | About 11 to 12 | Medium to large |
| 12 | About 1/2 to 5/8 | About 13 to 15 | Large |
| 14 to 16 | About 5/8 to 3/4 | About 16 to 19 | Large |
| 18 to 20 | About 3/4 to 7/8 | About 20 to 22 | Extra large |
| 24 | About 1 or more | About 25 or more | Extra large |
When you compare models, our list of the best filbert brushes for painters notes actual widths and hair types, which helps when sizes from different brands do not line up.
How to Read a Filbert Brush Label
A brush handle often carries more information than just the size. Knowing what each mark means helps you buy the right brush the first time.
- Brand and series number: Each series has its own sizing, hair type and shape. Two filberts from different series of the same brand can differ.
- Shape code: Some brands mark filberts with an abbreviation or symbol to distinguish them from flats, brights and rounds.
- Size number: Relative within that series; larger means wider and usually longer.
- Width in mm or inches: Not always printed, but when it is, it is the best way to compare across brands.
- Hair type: Hog bristle, synthetic, sable, mongoose or blends. This affects stiffness and paint load.
- Handle length: Long handles for easel painting in oil and acrylic; short handles for watercolor, gouache and close desk work.
Choosing Filbert Sizes by Canvas
The canvas sets the scale. A useful rule: your largest filbert should be able to block in the biggest shapes in a handful of strokes, and your smallest should handle the finest edges without switching to a liner.
| Canvas or paper size | Blocking-in filbert | Mid-stage filbert | Detail filbert |
|---|---|---|---|
| Up to 8 by 10 inches | Size 6 to 8 | Size 4 | Size 0 to 2 |
| 11 by 14 to 16 by 20 inches | Size 10 to 12 | Size 6 to 8 | Size 2 to 4 |
| 18 by 24 to 24 by 30 inches | Size 14 to 16 | Size 8 to 12 | Size 4 to 6 |
| 30 by 40 inches and larger | Size 18 to 24 | Size 12 to 16 | Size 6 to 8 |
A common mistake is starting too small. Large filberts encourage you to see big shapes and values first, which keeps the painting unified. Switch to smaller sizes only as you move toward details.
What Each Size Range Is Good For
Small filberts (sizes 0 to 4)
Small filberts handle detail with a softer edge than a round brush. They are useful for eyes, nostrils and the corners of lips in portraits; for small petals and leaves; for highlights on fruit and metal; and for refining edges where a round would leave a harsh line. In miniatures and small studies, a size 2 or 4 filbert can do much of the painting.
Medium filberts (sizes 6 to 10)
Medium filberts are the general-purpose range. They model forms in portraits and still lifes, build up foliage, paint clouds, and blend transitions between light and shadow. On typical 11 by 14 to 16 by 20 inch canvases, a size 6 or 8 filbert may be the brush you reach for most. Realist painters especially rely on this range; our guide to the best paint brushes for realistic painting explains how filberts fit alongside flats and rounds for that style.
Large filberts (sizes 12 and up)
Large filberts block in backgrounds, skies, large areas of skin and drapery, and broad landscape masses. Their rounded tip lets you lay down big strokes without the hard corners of a large flat, so transitions are easier to soften. They also make expressive, painterly strokes in loose and abstract work.
Filbert vs Flat vs Round: How Sizes Compare
Size numbers mean different things for different shapes, even within the same brand. A size 8 round is a pointed brush with a certain belly; a size 8 flat is a square-ended brush; a size 8 filbert sits between them.
| Shape | Tip | Mark at the same size | Best for |
|---|---|---|---|
| Round | Pointed | Narrow lines that swell with pressure | Lines, details, lettering |
| Flat | Square | Broad strokes with sharp edges and corners | Coverage, crisp edges, architecture |
| Bright | Square, shorter | Short, controlled strokes | Thick paint, impasto, control |
| Filbert | Rounded oval | Broad strokes with soft ends | Blending, organic shapes, portraits, florals |
Because filberts combine features of flats and rounds, many painters find they can replace one or two of each with a well-chosen set of filbert sizes.
Hair Type Changes How a Size Feels
- Hog bristle filberts are stiff and hold heavy oil and acrylic paint. Their sizes often run slightly wider because of the bristle’s natural flagging (split tips).
- Synthetic filberts range from firm to soft. Firm synthetics work well in acrylic; soft synthetics suit blending and glazing.
- Sable and other soft natural hair filberts are used for smooth blending in oils and for watercolor or gouache. They hold more liquid and lay down smooth, thin layers.
- Mongoose and blends sit between hog and sable in stiffness and are popular for oil portraits.
If you work across acrylic, collage and other mixed media, durable synthetic filberts are often the most practical choice; our roundup of paint brushes for mixed media in painting crafts covers brush sets that stand up to varied materials.
Five Strokes Every Filbert Size Can Make
Whatever size you pick, the same handful of strokes apply. Practicing them on scrap canvas with each size quickly shows how width changes the result.
- The flat pull. Hold the brush with the flat face against the surface and pull. You get a band of color as wide as the brush with soft, rounded ends. This is the blocking-in stroke.
- The edge line. Turn the brush 90 degrees so only the thin side touches, and pull. Even a size 10 filbert can draw a surprisingly fine line this way, useful for branches, hair strands and contour edges.
- The petal press. Press the flat face down and lift straight up. The oval tip leaves a petal or leaf shape. Rotating the brush between presses builds flowers quickly.
- The twist. Start on the flat face and roll the handle as you pull, ending on the edge. The stroke tapers from wide to thin, ideal for grass, feathers and the turn of a form.
- The feather blend. With a clean, nearly dry filbert, lightly drag the tip across the boundary between two wet colors. The rounded tip softens the transition without leaving a hard line.
Larger sizes exaggerate each stroke, while smaller sizes miniaturize them. Seeing the same five marks at size 2, size 8 and size 14 side by side is one of the quickest ways to decide which sizes your own work actually needs.
Building a Filbert Set
A three-brush starter set
For most canvases up to 16 by 20 inches: one small (size 2 or 4), one medium (size 6 or 8), and one large (size 10 or 12). This covers blocking in, modeling and refining.
A five-brush working set
Add an extra-small size 0 or 1 for fine details and a size 14 or 16 for large backgrounds. Many painters also keep two of their most-used size, one for lights and one for darks, to avoid muddying colors.
Paired sizes for blending
Some portrait painters keep a soft filbert one or two sizes larger than their working brush, kept clean and dry, for softening edges between strokes.
Filbert Sizing Mistakes to Avoid
- Buying by number alone. Check the width in mm or inches when comparing brands.
- Using only small sizes. Paintings done mostly with small brushes often look fussy and lack unity.
- Ignoring bristle length. Long filberts give more spring and softer marks; short ones give more control. The same size number can feel very different.
- Choosing soft hair for thick paint. Heavy impasto quickly bends soft filberts out of shape.
- Letting the tip wear flat. Filbert tips round down with use and can lose their shape. Clean gently and reshape after every session.
Caring for Filbert Brushes
- Wipe excess paint, then clean with the right solvent or water for your medium.
- Wash with brush soap, working paint out of the ferrule.
- Reshape the oval tip with your fingers while damp.
- Dry flat or bristles down.
- Avoid scrubbing filberts against the canvas, which wears the curve into a blunt edge.
FAQs
What is the most useful filbert brush size?
For many painters on mid-size canvases, a size 6 or 8 filbert is the most used. It blocks in shapes and handles modeling and blending.
Are filbert brush sizes the same across brands?
No. Each brand and series has its own scale. Compare listed widths in mm or inches, or measure the brush.
What size filbert brush should a beginner buy?
A small (2 or 4), medium (6 or 8) and large (10 or 12) cover most beginner projects on canvases up to about 16 by 20 inches.
How wide is a size 8 filbert brush?
Typically around 3/8 inch, or about 9 to 10 mm, though it varies by brand and hair type.
What is a filbert brush used for?
Blending, soft edges, organic shapes such as petals and leaves, portrait modeling, and broad strokes with rounded ends.
Is a filbert better than a flat brush?
Neither is better overall. Filberts give softer edges and blend easily; flats give crisp edges and sharp corners. Many painters use both.
Final Thoughts
A filbert brush size chart helps you translate handle numbers into real widths, but the canvas and the stage of the painting decide which size you actually need: large to block in, medium to model, small to refine. Compare widths rather than numbers when buying from different brands, and pay attention to hair type and bristle length. When you are ready to choose specific brushes, see our picks of versatile filbert brushes for oil and acrylic.
