.......Crochet Hook Sizes...............Metric...............Knitting Needle.
.....Aluminium...............Steel........
...U.S.........UK.......US.......UK.......Millimeter..........U.S........UK..
....-.........................14.........6..........0.60 mm.................................
....-.........................12.........5..........0.75 mm.................................
....-.........................10.........4..........1.00 mm..................................
....-..........................8..........3..........1.25 mm..................................
....-.............16.........7.........2.5.........1.50 mm.................................
....-.............15.........4..........2..........1.75 mm..................................
....-.............14.........1..........1..........2.00mm.............0............14....
B....1..........13.........0.........00.........2.50 mm............1............13....
C....2..........12.................................2.75 mm............2............12....
.....-............11........00.....................3.00 mm..........................11....
D....3..........10................................3.25 mm.............3...........10.....
E....4..............................................3.50 mm.............4....................
F....5...........9.................................3.75 mm.............5.............9.....
....-...............8................................4.00 mm...........................8.....
G....6............-................................4.25 mm..............6...................
-....7............7.................................4.50 mm..............7.............7.....
H....8...........6.................................5 mm...................8.............6.....
I.....9...........5.................................5.5 mm................9.............5.....
J...10.......... 4..................................6 mm.................10.............4.....
K..10 1/2....3..................................6.5 mm............10 1/2..........3.....
-.....-...........2..................................7 mm....................................2.....
-.....-............1.................................7.5 mm..................................1....
L.......11.......0.................................8 mm.................11..............0.....
M/N..13......00................................9 mm.................13.............00....
N/P...15.....000..............................10 mm................15............000...
.........17....0000.............................13 mm................17...........0000..
P/Q...19...00000............................15 mm................19.........00000..
Q..................-...............................16 mm..........................................
S...................-...............................19 mm................35.....................
and at my favorite site: a tabel and some measurement conversions:
http://cache.lionbrand.com/faq/97.html?language=
