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Knitting Needle Sizes Explained (With Size Conversion Chart)


Klara Nilsson | Updated on October 18, 2021

This knitting needle size guide contains everything you need to know on needle sizes, lengths, and measurements. You’ll find out how to choose the size of your needles based on yarn weight and convert needle sizes between different measurement systems.
knitting needles and yarn

If you’re starting a new knitting project, choosing the right needle size is essential. The size of your knitting needles affects how big your stitches are, which ultimately determines how big your project turns out.

Unfortunately, working out the right needle size isn’t always easy. Knitwear designers from all over the world use different measurements to indicate the recommended needle size, and vintage knitting patterns often use a different system altogether.

Knitting needles are usually measured by their diameter (the width of the circle), but some countries assign this measurement a random number, and some measure it in millimeters.

In this guide, we’ll explain everything there is to know about different knitting needle sizes, diameters, and lengths. We’ve also put together a handy size conversion chart to reference when you pick up a new project.

If you want to learn more about the different kinds of needles, check out our guide to knitting needle types and materials, instead.

What’s In This Guide?

Knitting Needle Size Conversion Chart

The size and diameter of knitting needles is typically measured using four main sizing systems: US, UK, Japanese, and metric.

Metric sizes are the easiest to convert to, and are most commonly found in patterns originating in Europe, Australia and New Zealand. US and Japanese sizes are almost identical, and UK sizes are also used in Canada.

Feel confused? Don’t worry! Use the chart below to convert different knitting needle sizes and find out exactly which needles you need for your project, yarn, or pattern. You can convert mm to US sizes and vice versa, in much more detail than most other conversion charts out there.

There is no direct conversion for the fields marked N/A. In this case, you’ll have to choose a size up or down and knit a tension square to check it works for you.

Metric Size (mm)US SizeUK/Canada SizeJapanese Size
1.0 mm0000019N/A
1.25 mm000018N/A
1.5 mm00017N/A
1.75 mm00N/AN/A
2.0 or 2.1 mm0140
2.25 mm113N/A
2.4 or 2.5 mmN/AN/A1
2.7 or 2.75 mm2122
3.0 mmN/A113
3.25 or 3.3 mm3104
3.5 or 3.6 mm4N/A5
3.75 mm59N/A
3.9 or 4.0 mm686
4.2 mmN/AN/A7
4.5 mm778
4.8, 5.0, or 5.1 mm869 or 10
5.4 or 5.5 mm9511
5.7 mmN/AN/A12
6.0 or 6.3 mm10413 or 14
6.5 or 6.6 mm10.5315
7.0 mmN/A2N/A
7.5 mmN/A1N/A
8.0 mm110N/A
9.0 mm130N/A
10.0 mm150N/A
12.0 mm17N/AN/A
16.0 mm19N/AN/A
19.0 mm35N/AN/A
25.0 mm50N/AN/A
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Old vs. New Knitting Needle Size Conversion

To make matters even more complicated, knitting needle sizes and sizing systems haven’t always been the same.

Older knitting needles and patterns usually came in smaller sizes. It’s often difficult to convert these measurements to metric sizes or the new US system, and trying to translate entire knitting projects can become a nightmare.

If you’re knitting a vintage pattern or you’ve inherited some old needles, this means you might need another handy conversion chart to know exactly where your needles stand in terms of sizing.

In this case, use the table below to convert old needle sizes to the new system. For reference, “dpn” stands for “double-pointed needles”.

Metric Size (mm)Standard US SizeOld US Size
1.0 mm0000018 (dpn)
1.125 mmN/A17 (dpn)
1.25 mm000016 (dpn)
1.5 mm00015 (dpn)
1.75 mm0014 (dpn)
2.0 mm00 (standard)
13 (dpn)
2.25 mm112 (dpn)
2.5 mmN/A1 (standard)
2.75 mm22 (standard)
11 (dpn)
3.0 mmN/A3 (standard)
10 (dpn)
3.25 mm3N/A
3.5 mm44 (standard)
9 (dpn)
3.75 mm55 (standard)
8 (dpn)
4.0 mm6N/A
4.25 mmN/A6 (standard)
4.5 mm7N/A
4.75 mmN/A7 (standard)
5.0 mm88 (standard)
5.25 mmN/A9 (standard)
5.5 mm9N/A
5.75 mmN/A10 (standard)
6.0 mm10N/A
6.5 mm10.510.5 (standard)
8.0 mm11N/A
9.0 mm13N/A
10.0 mm15N/A
12.0 mm17N/A
16.0 mm19N/A
19.0 mm35N/A
25.0 mm50N/A

Does Knitting Needle Length Matter?

As we’ve mentioned, most knitting needle measurements refer to the diameter of the needle (the width of the circle). This measurement determines the gauge and size of the stitches you create – but does the length of the needle matter too?

In short, the length of the needles you use makes absolutely no difference to the size of your stitches or the final outcome of the item you’re knitting. However, it can make a difference to how comfortable you are whilst you complete your project.

A large, heavy project like a big blanket will need longer needles (or cables) to carry the stitches. Small projects with relatively few stitches can be knit on any length of needle.

Straight needles tend to measure between 7 and 16 inches in length, though they can be longer. Circular needles use a cable that can vary in length up to approximately 60 inches, but the most common lengths are 16, 24, and 32 inches. In general, the more stitches you have, the longer your needles will need to be.

As a beginner, you should consider the length of your knitting needle. Listen to the pattern you’re knitting to know what to use. Most people find shorter needles more comfortable to hold, but longer needles allow more room for stitches along the length of the needle.

If you’ve been knitting for a long time, stick to what works for you. If you’re a brand new knitter, try out lots of different lengths and see how you feel!

Circular Needles and Needle Length

The length of your knitting needles might not be important for straight needles, but it is very important when it comes to knitting in the round with circular needles.

When knitting in the round, the diameter of the item you’re knitting is directly correlated to the length of the circular needles you’re using. The smaller the item, the shorter the circular needles you’ll need. Just make sure to check the knitting pattern for specifications!

Knitting Needle Sizes for Different Yarn Weights

When it comes to choosing needles for your next project, the knitting needle size you need will depend on the weight of the yarn you’re using. Generally speaking, heavier yarn will require wider needles.

Lace weight yarns will usually need needles between 1.5 and 2.5mm in diameter, worsted or middle-weight yarns will need needles between 3mm and 5.5mm, and chunky yarns will usually need 5mm to 8mm sized needles and larger.

While these are general guidelines, you might vary your needle sizes to produce certain textures or effects, or to achieve a specified gauge.

In most cases, the gauge listed on a pattern is in fact more important than the needle size. Remember to knit a test swatch and simply use the needle size necessary to knit the specified number of stitches per inch.

Yarn weight isn’t the only factor, remember: you’ll also have to consider the size, material, and texture of your project and find the needles that fit best.

In this section, we’ll go through each needle size and explain the types of yarn they’re typically used for.

Chunky, Super Chunky, and Bulky Yarn

Chunky, super chunky, and bulky yarn like Wool and the Gang’s Crazy Sexy Wool will almost always require large knitting needles. The average size of needle used with this type of wool is approximately 5mm – 8mm, with the smaller needles producing a tighter material.

chunky yarn
Chunky yarns are typically knit with wide needles.

This type of yarn and needle combination produces a thick knitted material that’s ideal for cold winter hats and sweaters. In fact, most of the designs in our list of bulky hat knitting patterns use exactly this type of needle and yarn.

You can also find even heavier yarn weights called jumbo yarn, which needs knitting needles sized around 12mm to 15mm. This type of combination is usually reserved for rugs, big blankets, and shawls.

If you’re interested in knitting up a project with chunky yarn, here are some perfectly-sized needle recommendations:

Medium-Weight and Worsted Yarn

This type of yarn is the most commonly-used amongst all types of projects. If you’re using medium-weight, Aran, or worsted yarn, you’ll probably require knitting needles sized between 3mm and 5.5mm.

worsted yarn
Medium-weight worsted yarn usually requires 3-5.5mm needles.

Scarves, vests, and cropped sweater knitting patterns all use this type of yarn and needle combination. Here are some recommendations:

Super-Fine, Fine, and Lace Yarn

Finer yarn means smaller needles. If you’re knitting up some socks or knitwear for a baby, it’s likely you’ll be using much thinner materials and creating much smaller stitches.

Light Weight Yarn
Light yarns like lace usually need the smallest needles possible.

In that case, you’ll probably need knitting needles between 1mm and 2.5mm in diameter.

Here are some great needle sets that are perfect for knitting with lace:

How Do I Know What Size Knitting Needles I Have?

A lot of modern knitting needles are labelled with their size – whether it’s written with the US, UK, or metric system. But not all of them are. This is especially a problem for vintage knitting needles.

If you’ve got too many needles to keep track of, or you’re unsure how large your needles are, you can use a very simple and affordable tool called a knitting needle gauge. If you’ve been knitting for a while, you’ve almost certainly already got one!

A needle gauge is simply a thin piece of wood or plastic with holes of different sizes, markings, and a ruler. To find out what size your knitting needles are, just slot your needles into the holes until you find a match.

If you don’t have a needle gauge, you can find the size of your needles using a normal ruler, as long as it uses the metric system. Simply place the wide end of the needle onto the millimetre side and measure the width of the needle.

Knitting Needle Size FAQs

What is the most commonly used knitting needle size?

The most common knitting needle size is US size 8, or 5mm. These needles are most common because they match up with worsted-weight yarn, which is the most common type of yarn for most knitting patterns. These needles are generally considered a normal size for beginners to start knitting with, too.

What happens if you knit with two different size needles?

If you knit a pattern using needles of different sizes, the yarn will develop regular holes known as the “torn stitch” effect. Some patterns use this technique deliberately, but be careful not to create this effect accidentally!

What is a good size knitting needle for beginners?

Medium sizes are generally the best for beginners. This means you should look for a width size of six (4mm), seven (4.5mm), or eight (5mm). For length, a 10-inch needle is usually a good starter size because they’ll be small enough to handle easily.

What happens if you use bigger knitting needles?

Simply put, larger knitting needles create larger stitches. A needle with a wide diameter will create larger loops when you wrap the yarn around it, which will increase the number of stitches you knit in an inch. Some designers like to use large needles for items like tote bags to create large, strong, airy stitches.  

What Is a Size 10 Knitting Needle in Millimeters?

US Size 10 knitting needles will measure between 6.0 and 6.3 mm. UK size 10 knitting needles will be sized between 3.25 and 3.3 mm.

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