By the way, do you know how to pronounce ‘sq’?
If you live an ordinary life, you probably haven’t even seen it, so few people might know.
‘sq’ is pronounced ‘square’. Square is a unit of wire thickness. One square approximately equals one square millimeter of cross-sectional area. ‘sq’ derived from the first two letters of ‘square’ because in English, it refers to ‘square millimeter’.
By the way, there are two types of wires: single wire and stranded wire, and only stranded wire uses the unit of ‘sq’. Single wire is expressed in diameter with mm (millimeters).
This unit ‘sq’ is defined by the JIS standard in Japan. In the United States, it is defined by the UL standard using the unit AWG (American Wire Gauge), while in Germany, it is defined by the DIN standard. Different countries have different standards and units, so they are not unified.
There are some troubles because the units are not standardized.

The wire stripper I use has numbers printed on both sides.
The left side shows AWG, and the right side shows MM. As explained earlier, AWG is the American standard. MM indicates the stripping hole diameter (φmm). Since there is no sq notation, when cutting a cable that is labeled in sq, I have to convert it to AWG in my head (e.g., a 0.3 sq cable would be cut at 22 AWG).
When I first started using wire strippers, I often cut too deep and damaged the core wire. Once you get used to it, you can tell the size just by looking.
In repairs, I always check if the size and allowable current are appropriate since the wiring materials used in foreign products and Japanese products differ in standards.
■ Examples of Standard Differences in Products Sold at Sound House
- Audio Cable
- Conductor: HC-OFC 0.4 sq
- Speaker Cable
- Conductor core wire: 1.31 mm² (16 AWG)
Let’s compare the cables from Oyaide and Belden.
Pay attention to the thickness notation. Oyaide uses 0.4 sq, while Belden uses 16 AWG. This difference is largely due to whether the product is Japanese or American.
Oyaide, with over 70 years of history, is a leading Japanese cable manufacturer and thus adheres to the JIS standard.
Belden, with over 100 years of history, is an American cable manufacturer and adheres to the UL standard.
It’s interesting to focus on these points and research the background of cables.
I compared these two brands just because it was easy to understand and there are no inherent advantages or disadvantages between different standards. Some products are labeled with both sq and AWG.
There are many other rare units, so I will introduce them if I get the chance.
Thank you for reading.