Like crochet hooks, knitting needle sizes are not universal. If you're knitting a pattern that has not been translated into English, you may find that the needle size is confusing. Depending on which country a pattern designer is from, you may have to do a little investigating to know which knitting needle size to use.
Why Converting Is Important
If you've ever seen a pattern from a country other than your own, you might notice that the supply list is a little different. A vintage U.K. pattern might call for a size 5 needle, for instance. If you use a U.S. size 5 needle on that pattern, you're going to get a surprisingly smaller result. The reason is because a vintage U.K. size 5 needle is 5.5mm, while the U.S. size 5 needle is 3.75mm.
Before you convert a knitting needle size, you'll need to find out the country of origin for the pattern. This will help you figure out which size system the country uses.
U.K. vs. U.S. Knitting Needles
The most common translation problem in knitting needle sizes is between the U.K. and the U.S.
Language is no indicator of whether the knitting needle size will be the same as your home country. For example, people in both the U.K. and U.S. speak English, but knitting terminology and needle sizes vary just slightly between them.
The year in which the pattern was published is another factor in converting needle sizes. Currently, the U.K. uses metric measurements. Sometimes these are already listed on your knitting needle; in that case, you shouldn't have a problem with conversion.
However, if you're knitting a vintage pattern, you will see a completely different U.K. needle numbering system. For current U.S. knitting needles, the needle number increases as the needle size increases. For example, a 5mm needle is a size U.S. 8 and the 5.5mm is a size U.S. 9. The opposite is true for vintage U.K. needles; the numbers decrease as the size of the needle increases. A 5mm needle is a size U.K. 6, and the 5.5mm is a size U.K. 5.
Note both the pattern's country of origin as well as the publication date when converting knitting needle sizes.
Using a Needle Gauge
Sometimes needles, especially circular needles, do not have the size clearly marked. In that case, you can use a needle gauge to figure out the size.
If the needle size is not clearly marked, do not guess at the size. The wrong size needle could negatively affect the gauge of your knitting.
Needle gauges are available in most craft stores where knitting needles are sold. To use the gauge, simply insert the needle into the holes of the gauge until you find a space that the needle fits in perfectly.
Using Conversion Charts
If the needle size is clearly printed on the needle, then using a conversion chart is the fastest way to convert the size. For example, if the pattern is from Australia and lists size 8mm, then refer to a conversion chart to see that the 8mm is equivalent to a U.S. size 11 needle.