Crochet reference

Crochet hook size chart

Every crochet hook size in one place: US letters and numbers to millimeters, steel hooks for thread, what an old pattern's "steel hook No. 10" means today, and old UK numbers. The millimeter size is the real one. Letters and numbers are labels, and they vary between makers.

Trust the millimeters

A 5 mm hook is 5 mm from any maker. An H-8 is usually 5 mm, but not always.

Steel hooks count backward

The bigger the number, the smaller the hook. A No. 14 is the finest; a No. 00 the largest.

Vintage numbers are a range

Old steel numbers were never one standard. Start with the size shown here and let your gauge decide.

Yarn hooks

US hook sizes to millimeters

Hooks for yarn, from the Craft Yarn Council hook chart. The old UK and Canadian number is shown where at least two published charts agree on it.

Metric	US	Old UK
2.25 mm	B-1	13 charts differ
2.5 mm	none	12 charts differ
2.75 mm	C-2
3.25 mm	D-3	10 charts differ
3.5 mm	E-4	9 charts differ
3.75 mm	F-5
4 mm	G-6	8 charts differ
4.5 mm	7	7 charts differ
5 mm	H-8	6
5.5 mm	I-9	5
6 mm	J-10	4
6.5 mm	K-10½	3 charts differ
7 mm	none	2
8 mm	L-11	0 charts differ
9 mm	M/N-13	00
10 mm	N/P-15	000
11.5 mm	P-16
12 mm	none
15 mm	P/Q
15.75 mm	Q
16 mm	Q
19 mm	S
25 mm	T/U/X
30 mm	T/X

Some Boye aluminum sets also have in-between sizes: D 3.125 mm, G 4.25 mm, I 5.25 mm, J 5.75 mm. So a Boye G can be a little bigger than a G-6.

Not sure which kind of hook to buy? See choosing a crochet hook: inline or tapered, handles, and hooks for sore hands.

Steel hooks

Steel crochet hook sizes today

Steel hooks are for crochet thread: doilies, lace and edgings. The two big US makers sell the same number at different sizes, so a Boye No. 10 is 1.3 mm and a Susan Bates No. 10 is 1.15 mm. If a pattern gives millimeters, go by those.

Number	Boye	Susan Bates
00	3.5 mm	2.7 mm
0	3.25 mm	2.55 mm
1	2.75 mm	2.35 mm
2	2.25 mm	2.2 mm
3	2.1 mm	2.1 mm
4	2 mm	1.75 mm
5	1.9 mm	not found
6	1.8 mm	not found
7	1.65 mm	1.5 mm
8	1.5 mm	1.4 mm
9	1.4 mm	1.25 mm
10	1.3 mm	1.15 mm
11	1.1 mm	1.05 mm
12	1 mm	1 mm
13	0.85 mm	0.9 mm
14	0.75 mm	0.7 mm

Boye sizes from Nancy Nehring and current Boye packaging; Susan Bates sizes from Antique Pattern Library and current Susan Bates packaging. The Craft Yarn Council steel chart lists two sizes for most numbers without naming makers; for 00 to 4 and 7 to 11 they are these two. It also gives a No. 5 and No. 6 of 1.7 and 1.6 mm, a No. 13 and No. 14 of 0.95 and 0.9 mm (larger than the Susan Bates 0.9 and 0.7), and a No. 12 of 0.6 mm, which we leave out. The Antique Pattern Library's Boye column gives No. 0 as 3 mm and No. 1 as 2.7 mm; Boye packaging today says 3.25 and 2.75.

Vintage steel hooks

What a vintage "steel hook No. 10" means today

Patterns from the 1910s to the 1960s give a steel hook number and no size. No pattern or catalog we found from that time states a diameter, so the honest answer is a range: from the smallest size any source gives for that number to the largest. Boye began selling steel hooks in 1917. The first ones were imported from England, and Boye first offered American-made steel hooks in December 1924. The sizes here are what Boye prints today. Start with those, the size our vintage patterns give, and expect an older hook to fall somewhere in the range.

Pattern says	Range	Start with
No. 00	2.7 to 3.5 mm	3.5 mm
No. 0	2.55 to 3.25 mm	3.25 mm
No. 1	2.35 to 2.75 mm	2.75 mm
No. 2	2.2 to 2.25 mm	2.25 mm
No. 3	2.1 mm	2.1 mm
No. 4	1.75 to 2 mm	2 mm
No. 5	1.7 to 1.9 mm	1.9 mm
No. 6	1.6 to 1.8 mm	1.8 mm
No. 7	1.5 to 1.65 mm	1.65 mm
No. 8	1.4 to 1.5 mm	1.5 mm
No. 9	1.25 to 1.4 mm	1.4 mm
No. 10	1.15 to 1.3 mm	1.3 mm
No. 11	1 to 1.1 mm	1.1 mm
No. 12	1 mm	1 mm
No. 13	0.75 to 0.95 mm	0.85 mm
No. 14	0.6 to 0.9 mm	0.75 mm

Ranges run across Boye and Susan Bates today, the Craft Yarn Council's second sizes and the Shire Album chart (1990). For No. 13 and No. 14 the Boye size sits inside the range, not at its top. Boye history from Nancy Nehring and Sylvia Landman.

Go by the thread

Thread is how makers chose a hook then, and it still works. A 1941 booklet paired its threads and hooks like this:

Thread	Steel hook
Mercerized crochet, size 10 or 20	No. 7 to 9
Mercerized crochet, sizes 30 to 50	No. 10 to 12
Knit-Cro-Sheen, bedspread cotton, Brita-Sheen	No. 6 to 8
Pearl cotton	No. 4 to 7
Brilliant	No. 6 to 8

From Old and New Favorites (Spool Cotton Company, 1941). A 1949 booklet from the same company used a No. 10 for size 30 thread and a No. 13 or 14 for size 70.

British patterns: double the number

On a British hook maker's catalog, the American number is twice the British one: a British No. 5 is an American No. 10, as on the Shire chart too. Not every chart agrees; Free Vintage Crochet pairs a British 4 with a US 7.

British	American	French
7	14	26
6 1/2	13	25
6	12	24
5 1/2	11	23
5	10	22
4 1/2	9	21
4	8	20
3 1/2	7	19
3	6	18
2 1/2	5	17
2	4	16
1 1/2	3	15
1	2	14

From the Alfred Shrimpton and Sons catalog (Redditch, after 1915), via Nancy Nehring. Many US pattern books from 1936 to 1956 named English-made hooks with American numbers, and those likely ran toward the smaller end of the range.

Old UK numbers

Old UK and Canadian hook numbers

Before metric sizes, UK yarn hooks had their own numbers, which also run backward; Free Vintage Crochet gives the same numbers for Canada. The charts agree from 6 to 4. From 13 to 7 they differ a little, by a quarter millimeter or by one number, so treat those as close, not exact.

Old UK	Metric
14	2 mm
13	2.25 mm charts differ
12	2.5 mm charts differ
11	3 mm charts differ
10	3.25 mm charts differ
9	3.5 mm charts differ
8	4 mm charts differ
7	4.5 mm charts differ
6	5 mm
5	5.5 mm
4	6 mm
3	6.5 mm charts differ
2	7 mm
1	between 7 and 8 mm
0	8 mm charts differ
00	9 mm
000	10 mm

From the Shire Album Crochet chart (Pauline Turner, 1990), Free Vintage Crochet, DMC and Antique Pattern Library. No crochet chart gives a millimeter size for old UK 1; the Shire chart places it between 7 and 8 mm.

Sources

Where these sizes come from

Every size on this page was read from one of these, checked November 12, 2026. Where they disagree, we say so.

More crochet guides

All crochet resources

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