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> > Hook size translated to mm, inches

JschoenAugust 15th, 2013, 10:20 am
Amherst, MA

Posts: 2
I've done some web research, can't seem to find a translation from hook size to millimeters or inches. I realize that there are a variety of hook models and manufacturers that lead to variability in hook size nomenclature.
When I think of hook sizes, my standard is the Mustad dry fly hook.
With that in mind, can anyone suggest how each hook size translates to mm? Inches is also useful.

Thanks.
TaxonAugust 15th, 2013, 1:07 pm
Site Editor
Plano, TX

Posts: 1343
Hi Jschoen-

The shank length of my Mustaad standard dry fly barbless hooks (94845) is as follows:

#10 - ~10 mm.
#12 - ~8.5 mm.
#14 - ~7 mm.
#16 - ~6.5 mm.
#18 - ~6 mm.

Hope this helps.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com
EntomanAugust 17th, 2013, 9:10 pm
Northern CA & ID

Posts: 2604
Hi Jschoen -

Welcome to the forum!

...can anyone suggest how each hook size translates to mm?

It can't be done as there is no industry standard to go by. There are dozens of styles from a bunch of different manufacturers now in common use and they are all a little different.

Back in the day, Mustad 94840's dominated the market to such an extent that using their designations was a good way to converse about the size of flies to use or the critters we tried to imitate. When an angler report mentioned a "14 PMD" on the water others knew what fly size to use. Those days are gone with the wind. As one example, below are the lengths of the popular Tiemco 100:

#12 - 10 mm
#14 - 8 mm
#16 - 7 mm
#18 - 6 mm

Using Mustad's sizing provided by Taxon as the bench mark for comparing the two, the TMC # 12's are really size 10's and the 16's are 14's. The TMC 14's are a size unto themselves - size 12.25? They only converge in shank length at size #18. Going down from there, the Tiemco's reverse the trend and begin to get smaller in length, though at all sizes there gaps are much bigger.

"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
SayfuAugust 21st, 2013, 3:37 pm
Posts: 560And I remember when all of that changing of the sizing took place. Japanese hook makers just added shank length to Mustad's hook size, and it won over a lot of tiers feeling they now had more room to apply material. Nifty bit of marketing.
EntomanAugust 21st, 2013, 3:49 pm
Northern CA & ID

Posts: 2604
You're so right, Jere. Then they touted "wide gap" designs for marketing purposes. First longer shanks then wider gaps. Hmmm... Can somebody explain the purpose of a long shanked wide gap 14 other than to cause confusion? Sounds like another way to describe a regular size 12 to me..:)LOL
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
EntomanAugust 21st, 2013, 4:01 pm
Northern CA & ID

Posts: 2604
BTW - What converted me was the wire quality, points, and barbs. Frankly, I like the consistent 1 mm spread between hook sizes. Below size 12 where a single mm can make a big difference, I wished they manufactured the odd sizes. What was interesting about the old Mustads was that on both sides of #16 the differences where a half mm. This covered the bulk of selectivity causing mayfly hatches with closer matches.
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
GutcutterAugust 21st, 2013, 6:47 pm
Pennsylvania

Posts: 470
...I like the consistent 1 mm spread between hook sizes. Below size 12 where a single mm can make a big difference...

With the tremendous variety in Tiemco hook styles, an exact size match to any fly, in any stage with any posture is just about a sure bet.

...I wished they manufactured the odd sizes...

Tiemco does.

...What was interesting about the old Mustads was that on both sides of #16 the differences where a half mm. This covered the bulk of selectivity causing mayfly hatches with closer matches...

Agree.
One of the problems anglers and fly tyers have, is the local jargon. A hatch chart listing "size 14 Hendrickson" can vary up to 3mm depending upon the hook manufacturer.
If I can't get a more accurate source, I'll tie a few emergers and duns in Tiemcos size 13, 14 and 15, then adjust once I'm there.
Rusty spinners? I already carry them in sizes 10-21...
All men who fish may in turn be divided into two parts: those who fish for trout and those who don't. Trout fishermen are a race apart: they are a dedicated crew- indolent, improvident, and quietly mad.

-Robert Traver, Trout Madness
EntomanAugust 21st, 2013, 10:04 pm
Northern CA & ID

Posts: 2604
Tiemco does.

Yes, but not in the same model. I was referring to the 100's. It would be cool if they made them in sizes 11 to 19 in addition to the even sizes. One can also mix and match with various models of other hook manufacturers as well. Daiichi makes some I do this with. I really don't know how many different models I use to tie various types and stages of mayfly, but there are a lot. Some would call us obsessed, Tony. :)

I remember a time when I imitated everything between 6 and 12 mm with two hooks, the Mustad 94840 and 3906B. We sure have more options now!:)
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
OldredbarnAugust 23rd, 2013, 11:40 am
Novi, MI

Posts: 2604
Great thread guys! You have re-visited an issue that bothers all us tiers...We all have probably tackled it in different ways...I have actually measured the working portion of the hooks and wrote the mm on the outside of the hook box. I then either use Justin Leonard's old book on Michigan Mayflies, or notes I've taken in the field over the years on the actual bugs length. I carry a small millimeter ruler I stole from my wife's sewing kit years ago...You didn't hear that here.

No one said it was going to be easy...

The guy that got me in to tying would always tell me to tie them in the size you think they are and then go one smaller...When I first started tying my bugs looked like they needed to go on a diet.

Mayfly abdomens, for the most part, are barely thicker than the hook shank. Old Nemes actually mic'ed some...Yes we can be a bit over-the-top from time to time. But we are having fun, right?! ;)
"Even when my best efforts fail it's a satisfying challenge, and that, after all, is the essence of fly fishing." -Chauncy Lively

"Envy not the man who lives beside the river, but the man the river flows through." Joseph T Heywood
MartinlfMarch 16th, 2022, 11:23 am
Moderator
Palmyra PA

Posts: 3192
Spence, and others, I spent some time researching hook shanks and fly sizes. As noted above there is no exact standard. This is what I'll be working with.

Fly sizes based on Caucci and other sources:

fly=mm actual TMC shank measurements from Flyhook.org

8= 12 12.47 mm shank on TMC 100 8 (long) ; tie short for true size 8 fly
10=11 11.22 mm shank on TMC 100 10 (close)
12= 9 9.80 mm shank on TMC 100 12 (long) ; tie v short for true size 12 fly
14= 8 8.27 mm shank on TMC 100 14 (close)
16= 7 7.99 mm shank on TMC 100 16 (v long) ; tie v short for true size 16 fly
18= 6 6.66 mm shank on TMC 100 18 (long); tie short for true size 18 fly
20= 5
22=4 4.91 mm shank on TMC 100 22
24=3.5 4 mm shank on TMC 100 24
26=3
28=2.5

Flyhook.org website actual measurements of TMC 921:
10=9.61mm close to TMC 100 12 (9.80), but slightly shorter
12=7.85mm close to two sizes shorter than TMC 100 so = TMC 100 16; actual size is closer to a size 14 fly.

Flyhook.org measurements TMC 102Y
13=8.45mm close to 100 14 (8.27) slightly longer; tie short for true size 14 fly
15=7.39mm between 100 18 (6.66) and 16 (7.99); tie short for true size 16 fly
17=6.12 may be close to 100 18 (6.66) but shorter; tie short for true size 18 fly
19=5.34

Roger R: The shank length of my Mustaad standard dry fly barbless hooks (94845) is as follows:

#10 - ~10 mm. shorter than TMC 100
#12 - ~8.5 mm. much shorter than TMC 100
#14 - ~7 mm. much shorter than TMC 100
#16 - ~6.5 mm. close to TMC 100
#18 - ~6 mm. shorter than TMC 100

Caucci Hatches II description of sizes for surface flies:
Fly size = body range mm (Caucci shows minimum fly sizes as equal to hook shank length; Caucci minimum fly sizes match fly sizes used at top for fly sizes 8-16; for smaller sizes 18 and 20, Caucci minimum is shorter.)

8= 12-14 12.47 mm shank on TMC 100 8; see notes at top
10=11-12.5 11.22 mm shank on TMC 100 10 (close)
12= 9-11 9.80 mm shank on TMC 100 12
14= 8-9.5 8.27 mm shank on TMC 100 14 (close)
16= 7-8 7.99 mm shank on TMC 100 16
18= 5-6 6.66 mm shank on TMC 100 18
20= 4.5-5
22=4-4.5 4.91 mm shank on TMC 100 18
24=3.5-4 4 mm shank on TMC 100 18
26=3-3.5
28=2.5-3

"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell
PartsmanMarch 17th, 2022, 1:57 pm
bancroft michigan

Posts: 419
Louis,thank you so much for the work you did here, this is going to be very helpful!
Mike.
MartinlfMarch 21st, 2022, 4:20 am
Moderator
Palmyra PA

Posts: 3192
You're very welcome, Mike. I found a few mistakes today with size 22 and 24 flies at the top and fixed them. Tight lines and good fishing to you this season.
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell

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