The picks
Best Size I Crochet Hook
Five and a half millimeters on two brands, 5.25 on a third - and one maker whose sets skip the size completely.
By Sawyer V. · Published November 9, 2026
Disclosure: we earn a commission when you buy through the links on this page, at no extra cost to you. It never decides what we recommend or how we rank it - read the full disclosure.
The short answer
Size I is 5.5mm - on Clover, which prints it as article 1048/I, and on Susan Bates, which lists its I as 5.5 mm. On Boye it is 5.25mm, printed on that company's own package. Two brands against one, which is the useful shape of the disagreement: buy on the millimeter and treat the letter as a label. There is a second thing worth knowing at this size and it is sharper than the usual letter problem. Boye's two ergonomic sets, between them, do not contain a 5.5mm hook at all - the light-and-medium set tops out at I/5.25mm and the bulky set starts at J/5.75mm, so the gap between them steps straight over 5.5mm. For one 5.5mm hook, the Clover Amour at article 1048/I is the sensible default; the Susan Bates Silvalume is the same size for considerably less, without a grip.
| # | Product | Best for | Published size | Grip | Price |
|---|---|---|---|---|---|
| 1 | Clover Amour Crochet Hook, I-9 (5.5mm)The Amour grip at the half step between H and J, printed with both the letter and the millimeter. | One 5.5mm hook for worsted at the size the ball bands name | I-9, 5.5mm (Clover) | Elastomer | $8.69 - View on Amazon |
| 2 |  Susan Bates Silvalume Crochet Hook, I-9 (5.5mm)A bare in-line aluminum hook at 5.5mm for the least money here, and the second brand confirming that I means 5.5mm. | Checking whether an in-line head suits you at this size | I, 5.5mm (Susan Bates) | None | $3.91 - View on Amazon |
| 3 |  Tulip ETIMO Rose Crochet Hook, 9/0 (5.5mm)The cushioned Japanese hook at 5.5mm - and unlike at 6mm, this size genuinely exists in the Rose line. | Long sessions, and anyone who finds the Amour grip too firm | 9/0, 5.5mm (Tulip) | Cushioned | $15.38 - View on Amazon#ad disclosure - price as of November 10, 2026 |
| 4 |  Brittany Birch Crochet Hook, I-9 (5.5mm), 7inBirch at 5.5mm, and the only hook here published at 7in rather than 5.5in. | Anyone who rests the hook in their palm rather than pinching it | I, 5.5mm (Brittany) | None - 7in birch | $16.67 - View on Amazon#ad disclosure - price as of November 10, 2026 |
| 5 |  Lantern Moon Ebony Crochet Hook, I (5.5mm)A single ebony hook at 5.5mm, for the yarns this size is most often used on. | Slippery yarn at a loose gauge | I, 5.5mm (Lantern Moon) | None - bare ebony | $18.20 - View on Amazon#ad disclosure - price as of November 10, 2026 |
| 6 |  Clover Amour Crochet Hook SetTen gripped hooks on one manufacturer's ladder, with I sitting in the middle of the range. | Anyone crocheting across more than one yarn weight | B/2.25mm to J/6.0mm | Elastomer | $48.56 - View on Amazon#ad disclosure - price as of November 10, 2026 |
| 7 |  Boye Ergonomic Crochet Hook Set, Light and Medium Yarn (40-40044)A four-hook set whose I is 5.25mm - and the top of a range that, with its sibling set, never reaches 5.5mm at all. | The sizes below I, where it is a perfectly good cheap set | I, 5.25mm (Boye) | Molded grip | $16.32 - View on Amazon#ad disclosure - price as of November 10, 2026 |
Clover Amour Crochet Hook, I-9 (5.5mm)
Clover · Best for one 5.5mm hook for worsted at the size the ball bands name
The Amour grip at 5.5mm - the half step between H and J, and the size three common yarn bands name outright.
- Size
- I-9 - Clover publishes 5.5mm
- Grip
- Elastomer rubber, latex free
- Shaft
- Aluminum
- Head
- Rounded, between inline and tapered
- Sold as
- One hook, one size
- Article
- 1048/I
Who it suits
Anyone whose pattern or ball band says 5.5mm or I-9, and anyone whose Amour set has lost exactly this hook.
Why it is here
Clover sells this as article 1048/I, Size I, 5.5mm, with the molded elastomer grip and the rounded head used across the Amour line. It is the default here for the same reason the H and J singles are: the package carries both numbering systems, which matters most at a letter brands disagree about. There is a second reason specific to this size - 5.5mm is what three of the yarns this site lists print on their own bands, so this is a hook patterns ask for by name rather than one you arrive at by swatching.
What you give up
Rubber grips perish over years in a way bare aluminum does not, and at roughly the price of the whole Boye four-hook set it is not the cheapest route to 5.5mm - only the most exact one.
Specifications from Clover 1048/I Amour crochet hook, Size I 5.5mm - retail listing. We have not handled this item - see how we pick.
Susan Bates Silvalume Crochet Hook, I-9 (5.5mm)
Susan Bates · Best for checking whether an in-line head suits you at this size
The bare in-line aluminum hook at 5.5mm, and the second published brand confirming that I means 5.5mm.
- Size
- I (5.5mm), per the listing
- Length
- 5.5in
- Head
- In-line (head sits flush with the shaft)
- Material
- Lightweight anodized aluminum
- Grip
- None - bare shaft
- Sold as
- One hook, one size
Who it suits
Anyone who crochets tightly, anyone on a budget, and anyone who wants a spare of the size they use most.
Why it is here
Listed as Size I, 5.5 mm, 5.5in, in lightweight anodized aluminum with Susan Bates' in-line head - the head sits flush with the shaft rather than projecting past it, so it slides into a tight stitch without a wider shoulder to force through. Its real importance on this page is evidential: it is the second published brand putting I at 5.5mm, which is what turns the disagreement at the top of this page from a coin flip into two against one.
What you give up
No grip at all, and 5.5mm is a worsted size - which means long sessions on blankets and garments with nothing but a bare 5.5in shaft between your fingers.
Specifications from Susan Bates Silvalume aluminum crochet hook 5.5in, size I (5.5mm) - retail listing. We have not handled this item - see how we pick.
Tulip ETIMO Rose Crochet Hook, 9/0 (5.5mm)
Tulip · Best for long sessions, and anyone who finds the amour grip too firm
The cushioned Japanese hook at 5.5mm, and - unlike at 6mm - this size does exist in the Rose line rather than only the Red.
- Size
- 5.5mm - sold as Japanese size 9/0
- Grip
- Cushioned rubber grip
- Line
- ETIMO Rose - the same line as the G and H singles this site lists
- Sold as
- One hook, one size
Who it suits
Anyone who already knows a soft grip helps, and anyone who owns the Rose set and wants a matching spare.
Why it is here
Sold as size 9/5.5mm - 5.5mm on the Japanese 9/0 numbering - with Tulip's cushioned rubber grip. Worth being precise, because this site had to be careful about it one size up: at 6mm the ETIMO Rose single does not exist and [the J page](/crochet-hooks/best-size-j-crochet-hook) uses the separate Red line instead. At 5.5mm the Rose does exist, so this is the same line as the [G](/crochet-hooks/best-size-g-crochet-hook) and [H](/crochet-hooks/best-size-h-crochet-hook) singles rather than an adjacent one.
What you give up
Roughly twice the Clover for a grip difference that is a preference, not an upgrade. It also carries no US letter anywhere on it, so it is easy to buy the wrong size shopping by number alone.
Specifications from Tulip Etimo Rose crochet hook, size 9/5.5mm - retail listing. We have not handled this item - see how we pick.
Brittany Birch Crochet Hook, I-9 (5.5mm), 7in
Brittany · Best for anyone who rests the hook in their palm rather than pinching it
A turned birch hook at 5.5mm, and the only hook on this size page whose published length is 7in rather than 5.5in.
- Size
- US I (5.5mm)
- Length
- 7in (18cm)
- Material
- Birch
- Handle
- None - the shaft is the handle
- Item
- 5063
- Sold as
- One hook, one size
Who it suits
Anyone who holds the hook overhand, and anyone whose hands get clammy on aluminum.
Why it is here
Brittany publishes this as item 5063, US size I (5.5mm), 7in (18cm), turned from birch with no separate handle. The length is the specification worth paying for: an overhand grip puts the tail of the hook into the palm, and an inch and a half of extra shaft is the difference between a handle you hold and one you pinch. [Best crochet hooks for a knife grip](/crochet-hooks/best-crochet-hooks-for-a-knife-grip) works through why that number matters. Birch also stays at hand temperature where aluminum does not.
What you give up
No grip section, so the diameter is whatever 5.5mm is - and a longer hook is worse, not better, for a pencil grip, where the tail has nowhere to go. Birch is softer than metal and can pick up a burr at the throat if it meets a zipper in a project bag.
Specifications from Brittany birch crochet hook 7in (18cm), size US I (5.5mm), item 5063 - retail listing. We have not handled this item - see how we pick.
Lantern Moon Ebony Crochet Hook, I (5.5mm)
Lantern Moon · Best for slippery yarn at a loose gauge
A single ebony hook at 5.5mm - the wooden option at the size where worsted starts to loosen off.
- Size
- US I (5.5mm)
- Material
- Ebony wood
- Format
- Single ended
- Sold as
- One hook, one size
Who it suits
Anyone working mercerized cotton, bamboo blends or silk, where stitches travel on a polished shaft.
Why it is here
Ebony, single ended, listed as US size I (5.5mm). The pairing is not incidental: Lion Brand's 24/7 Cotton - a mercerized cotton, and about as slick as worsted yarn gets - publishes 5.5mm as its hook. Ebony is dense and has surface texture where aluminum has none, so the loop stays where you put it. It is also the only pick here that is a pleasant object in its own right.
What you give up
Twice the Clover for a hook with no grip, so it does nothing for tired hands on a long project, and wood wants keeping dry - never wash it. Stock on this size runs thin; [best wooden crochet hooks](/crochet-hooks/best-wooden-crochet-hooks) covers the alternatives.
Specifications from Lantern Moon ebony single-ended crochet hook, US size I (5.5mm) - retail listing. We have not handled this item - see how we pick.
Clover Amour Crochet Hook Set
Clover · Best for anyone crocheting across more than one yarn weight
Ten aluminum hooks with a molded elastomer grip, covering 2.25mm to 6.0mm - the whole span most patterns for worsted and DK yarn ever ask for.
- Sizes
- 10 hooks: B/2.25mm to J/6.0mm
- Grip
- Elastomer rubber, latex free
- Shaft
- Aluminum
- Head
- Rounded, between inline and tapered
- Color coding
- Handle color differs per size
Who it suits
Anyone who works DK and worsted both, and anyone replacing a mixed-brand collection with one consistent scale.
Why it is here
Ten hooks, B/2.25mm to J/6.0mm, elastomer grip, rounded head, color coded by size. At this size in particular the set does something a single cannot: it puts H, I and J in the same box on the same ladder, so when a pattern sends you half a size up or down you are moving 0.5mm rather than moving between two brands' idea of a letter. The break-even against gripped singles lands around five sizes.
What you give up
It stops at J/6.0mm, and Clover's next gripped offering starts at 10mm - so nothing in this range covers the 6.5mm to 9mm sizes a chunky blanket wants.
Specifications from Clover USA product page. We have not handled this item - see how we pick.
Boye Ergonomic Crochet Hook Set, Light and Medium Yarn (40-40044)
Boye · Best for the sizes below i, where it is a perfectly good cheap set
Boye's tapered throat - the American reference for the geometry that grabs the whole strand - now sold only with an ergonomic handle on it.
- Head
- Tapered throat with a rounded head
- Set contents
- 4 hooks: F/3.75mm, G/4.25mm, H/5.0mm, I/5.25mm
- Suits
- Light and medium weight yarn, per the model name
- Shaft
- Anodized aluminum
- Handle
- Molded ergonomic grip, color-coded by size
- Model
- 40-40044
Who it suits
Nobody who came here needing a 5.5mm hook. Reasonable if you want F, G and H cheaply and with a grip.
Why it is here
Boye's own package art for the 40-40044 set prints its sizes as F/3.75mm, G/4.25mm, H/5.0mm and I/5.25mm. That I is a quarter of a millimeter under the 5.5mm Clover and Susan Bates both publish - and, unlike Boye's J, it is not simply a near-miss. 5.25mm sits exactly halfway between Clover's H at 5.0mm and Clover's I at 5.5mm, so it is a half-step hook that no other brand on this page makes.
What you give up
Buy it for F, G and H, where it is one of the cheapest ways to get a grip at all. Just do not buy it expecting 5.5mm, and if you already own one, measure before you swatch anything where gauge matters.
Specifications from Boye 40-40044 ergonomic hook set, sizes F/G/H/I - retail listing. We have not handled this item - see how we pick.
Three brands, three ladders
This site has now checked four letters against the makers' own published figures, and the pattern is consistent enough to act on: the US letter is a label, not a measurement.
| Letter | Clover | Susan Bates | Boye | Agree? |
|---|---|---|---|---|
| G | 4.0mm | Not published as a single | 4.25mm | No |
| H | 5.0mm | 5.0mm | 5mm | Yes |
| I | 5.5mm | 5.5mm | 5.25mm | No - two against one |
| J | 6.0mm | 6mm | 5.75mm | No - two against one |
I and J are the two letters where two brands agree against a third, which makes both of them clear cases rather than coin flips. If your pattern says 5.5mm, a Clover I and a Susan Bates I both are; a Boye I is not. A quarter of a millimeter is roughly half the step between neighboring hook sizes at this end of the scale, which is enough to miss a published gauge - and on a garment a missed gauge compounds across every row.
The size Boye's sets skip
This is the finding specific to I, and it is the reason this page exists rather than being a footnote on the H page. Read Boye's two ergonomic sets together and a hole appears exactly where 5.5mm should be.
| Set | Sizes | In millimeters | Reaches 5.5mm? |
|---|---|---|---|
| Boye 40-40044 (light and medium) | F, G, H, I | 3.75, 4.25, 5.0, 5.25 | No - stops 0.25mm short |
| Boye 40-40045 (medium and bulky) | J, K, L, N | 5.75, 6.5, 8, 10 | No - starts 0.25mm above |
Between 5.25mm and 5.75mm there is nothing. A crocheter who owns both Boye sets owns eight hooks spanning F to N - what looks like complete coverage of the working range - and does not own a 5.5mm hook. That is not true of any other letter this series has examined: Boye's G is a near-miss of Clover's G, its J is a near-miss of Clover's J, but its ladder genuinely steps over this size.
It follows that Boye's I is not a slightly-wrong I. At 5.25mm it sits exactly halfway between Clover's H at 5.0mm and Clover's I at 5.5mm - a true half-step, and a size no other brand here offers. Useful to know if you like it; a problem if you assumed it was a 5.5mm hook.
What 5.5mm is actually for
Yarn bands are the best evidence of what a manufacturer thinks a hook is for, and this is a size that gets named outright rather than inferred. Three of the yarns this site lists print it.
| Yarn | Weight | Published hook | Published crochet gauge |
|---|---|---|---|
| Red Heart Super Saver | 4 Medium / worsted | 5.5mm (US I/9) | 12 sc x 15 rows / 4in |
| Lion Brand 24/7 Cotton | Worsted | 5.5mm (US I/9) | 16 sc x 18 rows / 4in |
| Lion Brand Touch of Alpaca | 4 Medium / worsted | I-9 (5.5mm) | 14 sc x 18 rows / 4in |
Note how far apart those gauges are on the same hook: 12 single crochets to four inches in Super Saver against 16 in 24/7 Cotton. Same size, same stitch, and a third more stitches in the cotton - which is the clearest demonstration available that a hook size is an input, not an outcome.
- Worsted acrylic at a relaxed gauge. Red Heart Super Saver's band names 5.5mm, and a worsted acrylic at this size makes the soft, slightly open fabric blankets want.
- Mercerized cotton, where the band names 5.5mm and the fabric comes out crisp rather than loose - best hook for cotton yarn covers why cotton is hard on hands at any size.
- Hats and accessories in worsted, which is where a half step matters: 5mm for a firm brim, 5.5mm for a looser body. Best crochet hooks for hats treats hook size as the fit decision it is.
- Garments that need a little drape without going all the way to 6mm.
- Not amigurumi. At 5.5mm the stuffing shows through - that is a 3.5mm to 4mm job, covered on best crochet hooks for amigurumi.
Best crochet hook for worsted weight yarn approaches the same ground from the yarn side, across the whole band rather than this one size.
The length figure, and why it matters here
Most hook makers do not publish a total length, which makes the two on this page that do worth attention - particularly if you already know which grip you use.
| Hook | Published length | Handle | Suits |
|---|---|---|---|
| Brittany birch I-9 | 7in (18cm) | None - birch shaft | A knife grip, which rests the tail in the palm |
| Susan Bates Silvalume I | 5.5in | None - bare aluminum | A pencil grip, where a long tail is in the way |
| Clover Amour I | Not published | Elastomer | Either |
| Tulip ETIMO Rose 9/0 | Not published | Cushioned | Either |
| Lantern Moon ebony I | Not published | None - ebony shaft | Either |
An inch and a half is a large difference in the one dimension an overhand hold actually loads. If your hand sits on top of the hook, the Brittany is the pick here; if your hand sits beside it with the tail running back over your knuckles, the shorter Susan Bates is. Best crochet hooks for a knife grip and best crochet hooks for a pencil grip cover the two cases properly, and how to hold a crochet hook settles which one you use in a paragraph.
Numbering, one more time
The letter problem is not the only one. Three systems describe this hook, and two of them use bare numbers that look like millimeters and are not.
| System | This hook | Notes |
|---|---|---|
| US letter | I-9 | 5.5mm on Clover and Susan Bates, 5.25mm on Boye |
| Metric | 5.5mm | The only figure that cannot be misread |
| Japanese | 9/0 | Tulip sells its 5.5mm ETIMO Rose as size 9/5.5mm |
The same collision shows up here as at J: the US system writes this size as both I and 9, and the Japanese system writes it as 9/0. They happen to agree at this size, which they do not at every size, so a listing that says only 9 is still worth checking. The crochet hook size chart has the full letter-to-millimeter table.
Single or set
An honest page about one hook has to say when one hook is the wrong purchase.
A ten-piece gripped set spans 2.25mm to 6.0mm for roughly six times the price of one gripped single, so the break-even sits around five sizes - which anyone crocheting both garments and blankets passes inside a year. At this size the set earns its place for a reason beyond arithmetic: it puts H, I and J in one box on one maker's ladder, so moving half a size means moving 0.5mm rather than moving between two brands' idea of a letter.
Buy the single when 5.5mm is the size you actually use, when you want a material the set does not offer, or when you want a second copy of the hook a long project is running on - finishing a blanket on a different hook is a visible mistake. Hook sets vs single hooks has the arithmetic in full.
How we picked
Ranked on published size first, because that is the thing this category gets wrong and the reason this page exists, then on grip and head profile, then on price. Every figure comes from the manufacturer's own published product information or, where a maker publishes no figure, from the retail listing that does - all cited below, and the cells that say a figure is not published are cells where no maker publishes one. We have not held or crocheted with any of these hooks and make no claim about how they feel. How we pick explains the method.
Questions people actually ask
What size is an I crochet hook in mm?
5.5mm on most brands. Clover publishes its I as 5.5mm on article 1048/I and Susan Bates lists its I as 5.5 mm. Boye is the exception at 5.25mm, printed on the package of its 40-40044 set. Patterns that say I almost always mean 5.5mm.
What letter is a 5.5 mm crochet hook?
I, written as I-9 in the US system - the letter and the number name the same hook. In the Japanese system it is 9/0, which Tulip prints as size 9/5.5mm. The one brand that does not put I at 5.5mm is Boye, which publishes 5.25mm.
Is a size I hook 5.5mm or 5.25mm?
Both exist, which is the problem. Two brands publish 5.5mm and one publishes 5.25mm, and none is wrong - the US letter scale is not standardized between manufacturers. Match the millimeter your pattern gives rather than the letter.
Does Boye make a 5.5mm crochet hook?
Not in either of its ergonomic sets. The 40-40044 light and medium set runs F/3.75mm, G/4.25mm, H/5.0mm and I/5.25mm; the 40-40045 bulky set starts at J/5.75mm. Between them the range steps straight over 5.5mm, so owning both sets still leaves you without that size.
What yarn do you use with a size I crochet hook?
Worsted, mostly, at a slightly relaxed gauge. Red Heart Super Saver and Lion Brand 24/7 Cotton both print 5.5mm (US I/9) on the band, and Lion Brand Touch of Alpaca prints I-9 (5.5mm). It is the size for blankets, hats and garments that want a little drape without going to 6mm.
What is the difference between an H and an I crochet hook?
Half a millimeter - H is 5.0mm and I is 5.5mm on Clover and Susan Bates. In practice that is the difference between a firm worsted fabric and a relaxed one, which is why hat patterns so often specify one for the brim and the other for the body.
Should I buy a single I hook or a set?
A set if you will use three or more sizes - the break-even against gripped singles is around five, and a set keeps H, I and J on one manufacturer's scale. A single if 5.5mm is the size you actually use, or if you want a second identical hook for a long project.
Why do my stitches come out different sizes on the same hook?
Because the yarn changes the gauge, not just the hook. On the same 5.5mm hook, Red Heart Super Saver publishes 12 single crochets to four inches and Lion Brand 24/7 Cotton publishes 16 - a third more stitches in the same span. Always swatch in the yarn you are using.
Sources
- Clover 1048/I Amour crochet hook, Size I 5.5mm - retail listing
- Clover 1047/H Amour crochet hook, Size H 5.0mm - retail listing
- Clover 1049/J Amour crochet hook, Size J 6.0mm - retail listing
- Clover USA - Amour crochet hook set
- Susan Bates Silvalume aluminum crochet hook 5.5in, size I (5.5mm) - retail listing
- Susan Bates Silvalume crochet hook 5.5in, size J (6mm) - retail listing
- Boye 40-40044 ergonomic hook set, sizes F/G/H/I - retail listing
- Boye 40-40045 ergonomic hook set, sizes J/K/L/N - retail listing
- Tulip Etimo Rose crochet hook, size 9/5.5mm - retail listing
- Lantern Moon ebony single-ended crochet hook, US size I (5.5mm) - retail listing
- Brittany birch crochet hook 7in (18cm), size US I (5.5mm), item 5063 - retail listing
- Yarnspirations - Red Heart Super Saver specification
- Lion Brand - 24/7 Cotton specification
- Lion Brand - Touch of Alpaca specification