Knitting Needle Size Chart — US to mm

Identify an Unmarked Needle

A knitting needle size chart in US to mm only helps once you know which needle you are holding. Calibrate once, then hold the shaft against the circles below. The full conversion chart is underneath.

Calibration 96 PPI

Hold a bank card against the outline and drag until the widths match — every card is 85.6 mm wide.

Needle shaft, actual size

Sizes above 12 mm are omitted from the gauge — they are easy to read on a ruler. They are all in the table below.

Knitting Needle Size Chart: US to mm

This knitting needle conversion chart gives knitting needle sizes in mm against US numbers. Millimetres are the reliable measurement — US numbers repeat across different metric sizes, and some metric sizes have no US number at all.

Knitting needle conversion, millimetres to US size
Millimetres	US size	Typical yarn
1.5 mm	000	Lace, thread
1.75 mm	00	Lace, thread
2 mm	0	Lace, thread
2.25 mm	1	Fingering, sock
2.75 mm	2	Fingering, sock
3 mm	—	Fingering, sock
3.125 mm	3	Fingering, sock
3.25 mm	3	Fingering, sock
3.5 mm	4	DK, light worsted
3.75 mm	5	DK, light worsted
4 mm	6	DK, light worsted
4.25 mm	6	DK, light worsted
4.5 mm	7	DK, light worsted
5 mm	8	Worsted, aran
5.25 mm	9	Worsted, aran
5.5 mm	9	Worsted, aran
5.75 mm	10	Worsted, aran
6 mm	10	Worsted, aran
6.5 mm	10½	Bulky
7 mm	—	Bulky
8 mm	11	Bulky
9 mm	13	Bulky
10 mm	15	Super bulky, jumbo
12.5 mm	17	Super bulky, jumbo
12.75 mm	17	Super bulky, jumbo
15 mm	19	Super bulky, jumbo
19 mm	35	Super bulky, jumbo
25 mm	50	Super bulky, jumbo
35 mm	70	Super bulky, jumbo

Source: Craft Yarn Council, verified 5 August 2026. A dash means the size has no assigned US number.

How to Measure a Knitting Needle

Measure the shaft — the straight section the stitches slide along. Not the tapered tip, which is thinner, and not the join on a circular needle, which is usually thicker. The shaft diameter is what forms the stitch, and it is what the printed number refers to.

Calibrate the gauge above against a bank card. It takes ten seconds and is saved.
Lay the needle flat against the screen, shaft across the circles.
Find the circle the shaft covers exactly — not one it sits inside.

Below 4 mm, adjacent sizes are often 0.25 mm apart, which is difficult to judge against a ruler's markings. Matching an area is easier than reading a scale, which is why physical needle gauges exist at all — this is the same idea, on your screen.

Why US Numbers Repeat

The US system has fewer steps than the metric one, so several US numbers cover two metric sizes each:

US 3 — both 3.125 mm and 3.25 mm
US 6 — both 4 mm and 4.25 mm
US 9 — both 5.25 mm and 5.5 mm
US 10 — both 5.75 mm and 6 mm
US 17 — both 12.5 mm and 12.75 mm

That is a genuine ambiguity, not a chart error. Two needles both marked US 6 can differ by 0.25 mm, which is enough to shift your gauge. It is the reason patterns and yarn labels increasingly print millimetres, and the reason to trust the metric marking when the two disagree.

Three sizes in common circulation — 2.5 mm, 3 mm and 7 mm — have no US number at all. A chart that gives you one has invented it.

Needles and Hooks Are Not Interchangeable

A 4 mm knitting needle and a 4 mm crochet hook have the same diameter, but the numbering is completely different: 4 mm is US 6 as a needle and US G-6 as a hook. A gauge measures diameter correctly for both, but the size label beside the hole will only be right for one. Use the crochet hook chart for hooks.

Accuracy and Limits

Calibrate at 100% browser zoom, and recalibrate if you change it.
Look straight at the screen. Judging a circle edge at an angle introduces parallax.
Measure the shaft on a circular needle, never the cable or the join.

Calibrated carefully, the gauge separates adjacent sizes reliably. For a garment, it is still worth knitting a swatch — the needle size is a starting point, and the gauge you achieve is what actually decides the finished measurements.

Frequently Asked Questions

How do you tell what size a knitting needle is?

Measure the shaft, not the tip and not the join. The shaft is the straight section the stitches sit on, and its diameter is the number printed on a marked needle. Use the gauge above: hold the shaft against the circles and find the one it fills exactly.

How do I measure a knitting needle without a needle gauge?

Hold the shaft against a millimetre ruler, or compare it against a needle you have already identified. A ruler is awkward below 4 mm because adjacent sizes are often only 0.25 mm apart. Matching against a circle of known diameter, as the gauge above does, is more forgiving.

What size is a 2.5 mm knitting needle?

2.5 mm sits between US 1 (2.25 mm) and US 2 (2.75 mm) and has no assigned US number in the Craft Yarn Council standard. It is a common European and Japanese size. If a pattern calls for US 1 or 2 and you only have 2.5 mm, swatch before committing.

Does knitting needle size matter?

Yes — needle size is the main control over stitch size and therefore the finished dimensions. But what matters more is the gauge you actually achieve. Two knitters using the same needle and yarn routinely produce fabric that differs by a full size, so always swatch for a garment.

Why do US knitting needle numbers repeat?

Because the US system has fewer steps than the metric one. US 3 covers both 3.125 mm and 3.25 mm; US 6 covers 4 mm and 4.25 mm; US 9 covers 5.25 mm and 5.5 mm. That is a real ambiguity in the standard, and it is why patterns and yarn labels increasingly give millimetres.

Are US and UK knitting needle sizes the same?

No, and the old UK system runs backwards — a higher UK number means a thinner needle. UK 8 is 4 mm while US 6 is 4 mm. The UK numbering is legacy and inconsistently applied, which is why this chart gives millimetres and US sizes only. Measure the shaft rather than trusting a UK conversion.

What size needles for DK yarn?

DK weight is normally knitted on 3.75 mm to 4.5 mm — US 5 through US 7. Start at 4 mm and swatch. If the fabric feels stiff and dense, go up a size; if it looks loose and holey, go down.

Can I use a knitting needle gauge for crochet hooks?

Only partly. A gauge measures diameter, so it will read a hook's shaft correctly — but hooks and needles use different numbering, so the US size printed beside the hole will be wrong for a hook. Use the crochet hook chart for hooks and this one for needles.

What is the difference between US 10 and US 10½?

US 10 is 6 mm and US 10½ is 6.5 mm, so half a millimetre. It sounds trivial, but at that scale it is an 8% difference in diameter and it shows up clearly in gauge over a garment-sized piece. The half sizes exist because the gap between whole US numbers is large at this end.