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Quick reference

Round Brush Size Chart

Use the chart for a fast starting point, then filter it, compare starter patterns and jump into the finder when you want the full technique.

Most useful rule: start with hair length, then refine for shape. Smaller diameters mean more control and bend; larger diameters mean broader curves and looser volume.

Reviewed August 12, 2026US search intentMethodology & sources →

Fast answer

Pick a length and goal to highlight a starter range.

What the chart solves

Quick starting diameter by hair length and goal.

What the chart does not solve

Section size, airflow, direction and cooling.

Hair lengthHighlight goalUse the size finder

Hair length	Volume	Blowout	Smooth	Soft waves	Bangs
Pixie / very short	20–28 mm	25–32 mm	20–25 mm	20–25 mm	20–25 mm
Bob	32–38 mm	32–38 mm	25–32 mm	25–32 mm	20–28 mm
Chin to collarbone	38–45 mm	38–45 mm	32–38 mm	32–38 mm	25–32 mm
Shoulder length	45–55 mm	43–50 mm	38–45 mm	32–45 mm	25–38 mm
Long	50–65 mm	50–65 mm	45–55 mm	38–50 mm	25–38 mm

Practical starting ranges, not hard rules. Brush construction, actual barrel diameter, section size and technique can change the result.

Interactive diameter visualizer

See what changes as the barrel gets larger

Move from control and bend toward broader curves and looser volume. This is a visual learning tool, not a replacement for hair-length fit.

Barrel diameter38 mm

Use the slider to understand the tradeoff between control, bend and broad volume.

20 mm65 mm

ShapeVisible movementControlBalanced control

Useful for bobs, medium lengths, waves and controlled front sections.

25 recommendation cells

What the sizing model actually shows

These visuals are calculated from the same five hair-length × five styling-goal ranges shown in the table above. They are reference data, not invented user behavior.

Typical midpoint by hair length

Midpoint of the five goal ranges for each hair length.

Typical midpoint by styling goal

Midpoint across the five hair-length rows for each goal.

Shortest average

Bangs/front sections stay in smaller bands because control and barrel contact matter more than broad shape.

Largest average

Volume and blowout ranges expand as hair length increases.

Best use of the chart

Use it for the starting diameter; use the finder or method pages for the actual technique.

How to interpret a round brush size chart

Read the chart in two directions: start with your hair-length row, then move across to the styling goal. If your result is a range rather than one number, the smaller end gives more bend and control while the larger end gives a broader curve and looser volume.

Why “size 8” or “size 10” is not enough information

Numbered brush sizes are not standardized. A “size 8” from one brand can represent a different barrel diameter from another brand. That is why Round Brush Lab uses millimeters in the chart instead of relying on proprietary numbering.

Short, medium and long hair behave differently

Short hair: pixie and bob

Prioritize contact and control. Oversized barrels may not grip the section long enough to shape it.

Medium hair: chin to shoulder

This range is the most flexible: changing diameter and rotation can move the same length between smooth, bouncy and wavy finishes.

Long hair

Larger barrels work well for broad blowouts, while smaller sections or slightly smaller diameters add more visible movement.

What the chart cannot tell you

The chart does not know your section size, dryer angle, root elevation, moisture level or amount of rotation. Use the finder when you want those variables turned into an action sequence.

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