Find the millimeter size behind a US hook label, from B-1 to the larger hooks.
Metric first: US letters and numbers vary between manufacturers. A dash means the Craft Yarn Council does not list a US label for that metric size. This chart covers regular hooks, not steel thread hooks.
Find your size
Millimeters → US label
Crochet hook sizes
Metric diameter
US label
2.25 mm
B-1
2.5 mm
—
2.75 mm
C-2
3.125 mm
D
3.25 mm
D-3
3.5 mm
E-4
3.75 mm
F-5
4 mm
G-6
4.25 mm
G
4.5 mm
7
5 mm
H-8
5.25 mm
I
5.5 mm
I-9
5.75 mm
J
6 mm
J-10
6.5 mm
K-10½
7 mm
—
8 mm
L-11
9 mm
M/N-13
10 mm
N/P-15
11.5 mm
P-16
12 mm
—
15 mm
P/Q
15.75 mm
Q
16 mm
Q
19 mm
S
25 mm
T/U/X
30 mm
T/X
No matching size. Try a metric number or clear the filter.
Check the metric diameter on your hook or its packaging, then find that measurement in the chart. US letters and numbers are useful references, but their meaning can vary between brands. A label on its own is not an exact conversion.
Then make a swatch
A hook size is a starting point. Make a gauge swatch with your yarn and compare it with your pattern before committing to the whole project. Your stitches, yarn, and hook all play a part in the finished size.
What about steel hooks?
Small steel hooks for crochet thread use a different numbering system. They are outside this chart; do not use these US labels to convert a steel-hook number.