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Interdental brush sizes are numbered ISO 0 to ISO 8, and the number on the pack is the one to trust. The colour on the handle is not standardised: each supplier chooses its own. This page gives one manufacturer’s chart, labelled as such, and explains what the ISO number is actually measuring.
General product information only, not dental or medical advice.
Interdental brush size chart (one manufacturer’s)
The chart below is TePe’s Original interdental brush range, as listed on TePe’s professional product page (checked 2026-10-31). The colours are TePe’s own colour code, not an ISO colour. TePe does not say which measurement its millimetre figures describe, so they are not shown as passage hole diameter.
| TePe colour | ISO size on the pack | Size (mm) as listed by TePe |
|---|---|---|
| Pink | 0 | 0.4 |
| Orange | 1 | 0.45 |
| Red | 2 | 0.5 |
| Blue | 3 | 0.6 |
| Yellow | 4 | 0.7 |
| Green | 5 | 0.8 |
| Purple | 6 | 1.1 |
| Gray | 7 | 1.3 |
| Black | 8 | 1.5 |
Check your product’s labelling: a different brand’s yellow or blue may not match these numbers.
How to read the size number
ISO sizes follow ISO 16409:2016, which covers round-headed interdental brushes with a wired stem (see interdental brushes for the scope). In a 2020-listing study of the commercial range, the size is set by the passage hole diameter (PHD): the smallest hole through which a brush can pass without bending. A bigger ISO number means a brush that needs a wider gap.
Two points from the same study matter when comparing packs. All brushes with a PHD of 2.9 mm or more are classed as ISO size 8. And ISO sizes 1 to 3 each cover 2 PHD sizes, sizes 4 and 5 cover 3, and sizes 6 and 7 cover 5, so two brands can both print the same ISO number and still differ slightly in measured size.
How ISO size is measured
In the study’s method, the PHD is found with a standardised measuring plate 2.0 mm thick (plus or minus 0.1 mm) with holes in 0.1 mm steps. Eight samples of a brush are passed through descending hole sizes with a clinically relevant force, and the result is the smallest hole passed without bending. The study found commercial brushes spanning a PHD of 0.6 to 5.2 mm, with 90% at 2.0 mm or below.
Colour and millimetre equivalence notes
- Colour is supplier-specific. The study reports that colour coding was specific to each supplier. Read the ISO number on the pack rather than relying on colour.
- Labelling is inconsistent. Only about a third of manufacturers stated the ISO size, 25.0% gave the PHD, 79.2% gave the brush diameter and 45.8% gave the wire diameter. The study concluded that classification and labelling systems are highly diverse.
- A millimetre figure needs a definition. Brush diameter, wire diameter and PHD are three different measurements. Compare like with like.
Common mix-ups
- Treating the handle colour as a standard. Handle colour is supplier-specific (per the 2020-listing study), not a standard; use the printed ISO number.
- Reading the brush head width as the ISO size. The ISO size is the passage hole diameter, not the head or wire width.
- Confusing wired brushes with soft picks or floss. Those are different products; see interdental picks and dental floss types.
FAQ
What size interdental brush do I need?
This page cannot size a brush for any individual. It explains how the ISO number is defined and how to read a pack; a dentist or dental hygienist is the person to ask about your own teeth.
What do the ISO numbers on interdental brushes mean?
They group brushes by passage hole diameter, from ISO 0 (smallest) to ISO 8, where ISO 8 is any brush with a PHD of 2.9 mm or more.
Is the colour of the handle the same across brands?
No. Colour coding is specific to each supplier, so read the ISO number on the pack.
How do interdental brushes compare with floss?
Both clean between teeth; see dental floss types and interdental brushes for what each is and how products differ.
Sources
- TePe, Interdental Brush Original, professional product page: https://pro.tepeusa.com/products/tepe-interdental-brush-original (checked 2026-10-31).
- Mapping the Product Range of Interdental Brushes: Sizes, Shapes, and Forces, Oral Health Prev Dent: https://pmc.ncbi.nlm.nih.gov/articles/PMC11654537/ (checked 2026-10-31).
- ISO 16409:2016, Dentistry, Oral hygiene products, Manual interdental brushes; scope as described on our interdental brushes guide.
