Needle sizes
Just like yarn weights have different names around the world, needle sizes are also labeled differently depending on the system being used. And as with yarn, there’s not much consistency here either—so get ready for a bit of confusion! The chart below doesn’t cover every possible needle size, but it will give you a general idea.
In the metric system, the needle numbering begins with the smallest sizes, starting around 2.00mm. While there are even smaller needles, they’re less common. From there, the numbers increase in increments of either 0.25mm or 0.5mm, reaching up to around 25mm for extra thick needles meant for super chunky yarns.
The US system starts with a 0 numbered needle, equivalent to a 2.0mm metric needle. In the UK, this is a 14.
The US needle sizing goes up in (mainly) single digit increments, until a 50 needle is reached. This is equivalent to a 25mm metric needle size. The UK, however, goes down in number from 14 to 000. This 000 needle is equivalent to a 10mm metric needle.