Kanülengrößen und Farbcode nach ISO 6009

Cannula Sizes and Colour Code (ISO 6009): The Overview

3 min reading time

Single-use cannulas are colour-coded according to their outer diameter; this assignment is governed by the ISO 6009 standard. The colour at the cannula hub indicates the nominal outer diameter, which is traditionally also stated in Gauge (G). For example, 0.90 mm corresponds to 20G and the colour yellow. The labelling on the packaging always remains decisive.

What do Gauge and the colour code mean?

The Gauge value (G) is a traditional unit of measurement for the outer diameter of a cannula. As a general rule: the higher the Gauge number, the smaller the outer diameter. A 27G cannula is therefore thinner than a 20G cannula. In German-speaking regions, the size is frequently also stated as length × diameter in millimetres, for example "0.90 × 40 mm". Here, the first value usually describes the diameter and the second the length of the cannula.

The colour coding of the cannula hub (cone) is intended to enable quick visual orientation regarding the outer diameter. The ISO 6009 standard specifies which colour is assigned to which nominal outer diameter. Important: the colour does not replace the check of the printed size specification. The standard itself expressly notes that the colour coding does not release the user from the obligation to verify the stated size.

Colour code overview according to ISO 6009

The following overview shows common sizes from the range defined in ISO 6009 (in total from 0.18 mm to 3.4 mm). It serves as orientation; for the binding specification, always refer to the product and packaging labelling.

Outer diameter (mm)	Gauge	Colour according to ISO 6009
0.40	27G	Medium grey
0.45	26G	Brown
0.50	25G	Orange
0.55	24G	Medium violet
0.60	23G	Deep blue
0.70	22G	Black
0.80	21G	Deep green
0.90	20G	Yellow
1.10	19G	Cream
1.20	18G	Pink

Note: the colour refers exclusively to the outer diameter, not to the length of the cannula. Cannulas with the same diameter but different lengths therefore carry the same colour code. Because colour shades can vary in nuance across manufacturers and individual colours occur more than once across the full standard range, the selection should always be made on the basis of the specific size specification.

Selecting the right size

The suitable cannula size depends on the respective application, the viscosity of the solution and the individual circumstances. The decision is made by qualified medical personnel on their own responsibility, based on the product information and the clinical indication. When purchasing, pay attention to clear specifications regarding diameter, length and bevel, as well as conformity with the relevant product standards. You will find a selection of cannulas and matching accessories in our Single-Use Syringes & Injection category.

Frequently Asked Questions

What colour is a 20G cannula?

A cannula with an outer diameter of 0.90 mm corresponds to 20G and is colour-coded yellow according to ISO 6009. The binding specification is always stated on the packaging.

What does the Gauge specification (G) mean?

Gauge is a traditional unit of measurement for the outer diameter. The higher the Gauge number, the smaller the diameter of the cannula. The size is frequently also stated in millimetres as diameter × length.

Is the colour code identical across all manufacturers?

The assignment of outer diameter to colour is governed by ISO 6009. Colour shades can vary in nuance, which is why the printed size specification is always decisive, not the colour alone.