Knitting Needle Sizes: US, UK and Metric Conversion Chart

A knitting needle's size is its diameter: the thickness of its shaft, the straight part below the tapered tip. The same needle can carry three different labels depending on where and when it was made, which is why sizes cause so much confusion. The chart below lines them up.

Knitting needle size conversion chart

A dash (—) means there is no direct equivalent in that system. The US sizes 1½ and 2½ are not part of the official US sizing; some needle makers use them for 2.5 mm and 3 mm, and others do not.

Why millimeters are the measurement to trust

A metric size is a direct measurement: a 4 mm needle is 4 millimeters across. US and old UK sizes are names attached to those diameters, and as the gaps in the chart show, they do not line up neatly. That is why modern needles and patterns generally give the metric size, often next to the US size, and why it is the number to check first.

When you buy needles for a pattern, match the millimeters. If the pattern gives only a US size, use the chart to find the metric equivalent.

Old UK sizes run backward

Before metric sizes were adopted in Britain, needles there were numbered with an old wire gauge system, in which a higher number means a thinner wire. An old UK 14 is therefore a slender 2 mm needle, and an old UK 000 is a thick 10 mm one. US sizes work the other way around: the higher the number, the thicker the needle.

How to read needle sizes in a vintage pattern

Older British patterns, and patterns from countries that used British sizing, often give needle sizes as plain numbers, such as "No. 10 needles". The danger is reading them as US sizes:

• An old UK 8 is 4 mm, but a US 8 is 5 mm.
• An old UK 10 is 3.25 mm, but a US 10 is 6 mm.

To work from a vintage pattern:

1. Find out where the pattern was published and, roughly, when.
2. If it uses British sizing, look up each number in the "Old UK" column.
3. Write the millimeter size next to it on your copy.
4. Knit a gauge swatch before you begin, since your yarn is unlikely to be the one the pattern was written for.

Types of knitting needles

Straight needles

Straight needles have one point and a knob at the other end to stop stitches sliding off. They are used for flat knitting, worked back and forth in rows. They are often sold in lengths of about 10 in (25 cm) and 14 in (35 cm). Shorter needles are lighter and easier to handle; longer ones hold wider pieces.

Circular needles

A circular needle is two short tips joined by a flexible cable. It is used for knitting in the round, which makes seamless tubes such as hats and sweater bodies. It can also knit flat: you simply turn the work at the end of each row, and the weight of the piece rests in your lap instead of on your wrists.

The length is measured from tip to tip, cable included. For knitting in the round, choose a needle slightly shorter than the circumference of your piece, so the stitches reach all the way around without stretching: 16 in (40 cm) is the usual length for hats, and 24 in (60 cm) or longer suits sweater bodies. A long circular, 32 in (80 cm) or more, can also knit small tubes using the magic loop method, in which the extra cable is pulled out in a loop between stitches.

Interchangeable sets let you screw different tips onto cables of different lengths.

Double-pointed needles

Double-pointed needles, often shortened to DPNs, have a point at each end and come in sets of four or five. They knit small tubes, such as socks, mittens and the top of a hat. The stitches are divided over three or four needles, and you knit with the spare one. Common lengths are about 6 in (15 cm) and 8 in (20 cm).

Needle materials and how they feel

• Metal needles are smooth and slick, so stitches glide quickly. Experienced knitters often enjoy the speed, but beginners may find stitches sliding off before they are ready. Metal can also feel cold and make a clicking sound.
• Wood and bamboo needles are warm and light, with a gentle grip that keeps stitches in place. That grip makes them a comfortable choice for beginners. Very thin wooden needles can bend or snap if you sit on them.
• Plastic needles are light and have some grip. Large sizes are often made of plastic because metal or wood would be heavy; thin plastic needles can bend.

Tip shape matters too. Sharp points slip easily into tight stitches and suit fine yarns; rounder points are less likely to split thick, soft yarns.

How needle size relates to yarn weight

Thick yarn needs thick needles, and thin yarn needs thin ones. Every yarn label recommends a needle size, and that is your starting point. As a guide, medium-weight yarn, often called worsted or aran, is usually knitted on needles of about 4.5 to 5.5 mm (US 7 to 9).

Needles much smaller than recommended make a dense, stiff fabric. Needles much larger make a loose, open one. Patterns sometimes go outside the label's range on purpose, for example a larger needle for an airy shawl or a smaller one for firm, hard-wearing socks. Our yarn guide explains yarn weights in more detail.

Needle size, gauge and why you should swatch

Gauge, called tension in British patterns, is the number of stitches and rows in 4 inches (10 cm) of knitting. A pattern states the gauge its designer achieved; the needle size it gives is simply what the designer used. Every knitter holds the yarn a little differently, so the same needle can give different results in different hands. Matching the gauge is what makes your piece come out the size the pattern promises.

To knit and measure a swatch:

1. Cast on enough stitches for a square at least 6 in (15 cm) wide, using the pattern's yarn and needle. The pattern's gauge tells you roughly how many.
2. Work the stitch the gauge is given in, usually stockinette, until the piece is about 6 in (15 cm) tall.
3. Bind off loosely.
4. Wash and dry the swatch the way you will treat the finished item.
5. Lay it flat without stretching it.
6. Count the stitches across 4 in (10 cm) in the center of the swatch.
7. Count the rows over 4 in (10 cm) the same way.

If you have more stitches than the pattern, your stitches are too small: try a larger needle. If you have fewer, try a smaller needle. Change one size at a time and swatch again.

How to identify an unmarked needle

A needle gauge is a flat card of metal or plastic with a row of holes, each labeled with a size. Many also include a ruler and a small window for counting stitches on a swatch.

1. Hold the needle by its shaft, below the tapered tip. For a circular needle, measure a tip, never the cable.
2. Push the needle into a hole that looks about right.
3. Try smaller holes until you find the smallest one the shaft slides through without forcing.
4. Read the size printed beside that hole.
5. Label the needle, for example with a small tag, so you never need to measure it again.

What to learn next

Now that you can read any needle size, choose a yarn to go with it in our guide to beginner yarn, or put your needles to work with one of our easy first projects. For step-by-step lessons, explore the library.