What size is an H crochet hook in mm?

An H-8 hook is 5 mm. The old UK number for 5 mm is 6.

What is a G hook in mm?

G-6 is 4 mm. Some brands also label a 4.25 mm hook G, so check the millimeters printed on the handle.

What size is an I or J hook?

I-9 is 5.5 mm and J-10 is 6 mm. Some brands sell a 5.25 mm I and a 5.75 mm J.

What does an old UK hook number mean?

Old UK numbers run backwards: the bigger the number, the thinner the hook. A 14 is 2 mm, an 8 is 4 mm and a 000 is 10 mm. Patterns from before metric sizes use them.

Are crochet needle sizes the same as hook sizes?

Yes. “Crochet needle” is another name for a crochet hook, and the sizes are the same millimeters. Knitting needles use the same millimeters, so a 5 mm needle and a 5 mm hook have the same diameter.

My hook has no size on it. How do I find it?

Push the shank, the straight part just below the hook’s throat, through the holes of a needle gauge: the size is the smallest hole it passes through without forcing. Then mark that size in the chart.

Is a steel hook 10 the same as a 10 mm hook?

No. In the Craft Yarn Council steel table a 10 is 1.3 mm or 1.15 mm, and one older scale also uses 10 for a 0.75 mm hook, so the number alone does not fix the size. Steel numbers get larger as the hook gets thinner: buy by the millimeters printed on the hook.

Crochet hook size chart: mm, US letters, steel and old UK

Find your hook by the millimeters on its handle, then read its US letter, US number and old UK number in the same row. Tap a size to mark your hook.

Em português tabela de agulhas de crochê

My hook is

Millimeters first. US labels: Craft Yarn Council. Old UK numbers: DROPS hook chart.

Crochet hook sizes in millimeters, US and old UK
US letter and number	Old UK	Yarn weight it suits
–	14	–
B-1	–	0 Lace, 1 Super Fine
–	12	1 Super Fine
C-2	–	1 Super Fine
–	11	1 Super Fine
D	–	1 Super Fine
D-3	–	1 Super Fine
E-4	9	1 Super Fine, 2 Fine
F-5	–	2 Fine
G-6	8	2 Fine
G	–	2 Fine
7	7	2 Fine, 3 Light
H-8	6	3 Light
I	–	3 Light
I-9	5	3 Light, 4 Medium
J	–	4 Medium
J-10	4	4 Medium
K-10.5	3	4 Medium, 5 Bulky
–	2	5 Bulky
L-11	0	5 Bulky
M/N-13	00	5 Bulky, 6 Super Bulky
N/P-15	000	6 Super Bulky
P-16	–	6 Super Bulky
–	–	6 Super Bulky
P/Q	–	6 Super Bulky, 7 Jumbo
Q	–	7 Jumbo
Q	–	7 Jumbo
S	–	7 Jumbo
T/U/X	–	7 Jumbo
T/X	–	7 Jumbo

A dash means no standard label at that size. US letters vary between brands: a G can be 4 or 4.25 mm. Yarn weights are the Craft Yarn Council’s suggested hook ranges for each category; your swatch decides.

Steel crochet hooks for thread

Steel hooks have their own numbers, and they run backwards: the larger the number, the finer the hook. Brands use different scales, so one number can mean more than one diameter. Choose by millimeters.

Steel hooks: millimeters and the US steel numbers listed for them by the Craft Yarn Council
Millimeters	US steel number
3.5 mm	00
3.25 mm	0
2.75 mm	1
2.7 mm	00
2.55 mm	0
2.35 mm	1
2.25 mm	2
2.2 mm	2
2.1 mm	3
2 mm	4
1.9 mm	5
1.8 mm	6
1.75 mm	4 or 0
1.7 mm	5
1.65 mm	7
1.6 mm	6
1.5 mm	8 or 7 or 2
1.4 mm	9 or 8
1.3 mm	10
1.25 mm	9 or 4
1.15 mm	10
1.1 mm	11
1.05 mm	11
1 mm	12 or 6
0.95 mm	13
0.9 mm	14 or 8
0.85 mm	13
0.75 mm	14 or 10
0.6 mm	12

Convert a size from your pattern

Your hook size

5 mm

US H-8

Old UK 6

Match the diameter printed on the hook or package.

Why a letter is not always enough

A US G hook may be 4.0 or 4.25 mm. When more than one match appears, use the millimeter marking on the hook or the pattern designer's gauge. A larger hook generally makes larger stitches, but make a swatch to test the fabric.

Common questions

What size is an H crochet hook in mm?: An H-8 hook is 5 mm. The old UK number for 5 mm is 6.
What is a G hook in mm?: G-6 is 4 mm. Some brands also label a 4.25 mm hook G, so check the millimeters printed on the handle.
What size is an I or J hook?: I-9 is 5.5 mm and J-10 is 6 mm. Some brands sell a 5.25 mm I and a 5.75 mm J.
What does an old UK hook number mean?: Old UK numbers run backwards: the bigger the number, the thinner the hook. A 14 is 2 mm, an 8 is 4 mm and a 000 is 10 mm. Patterns from before metric sizes use them.
Are crochet needle sizes the same as hook sizes?: Yes. “Crochet needle” is another name for a crochet hook, and the sizes are the same millimeters. Knitting needles use the same millimeters, so a 5 mm needle and a 5 mm hook have the same diameter.
My hook has no size on it. How do I find it?: Push the shank, the straight part just below the hook’s throat, through the holes of a needle gauge: the size is the smallest hole it passes through without forcing. Then mark that size in the chart.
Is a steel hook 10 the same as a 10 mm hook?: No. In the Craft Yarn Council steel table a 10 is 1.3 mm or 1.15 mm, and one older scale also uses 10 for a 0.75 mm hook, so the number alone does not fix the size. Steel numbers get larger as the hook gets thinner: buy by the millimeters printed on the hook.

Print this chart to keep beside your hooks. Match a hook to your yarn weight, then choose the hook type and handle for your project →

Old UK numbers checked against the DROPS hook chart on October 9, 2026. Sizes without an old UK number in that chart show a dash rather than a guess.