Crochet Hook Sizes UK: The Complete Conversion Chart Guide

Right, let’s talk about crochet hook sizes because this genuinely confuses everyone when they’re starting out. You pick up a pattern, and it says “use a 4mm hook,” but your hook says “G-6” on it. Or you’ve inherited your nan’s old hooks and they just have a random number stamped on the side that doesn’t seem to match anything modern. When I started crocheting last year, I spent the first week using whatever hook came nearest to me out of the starter kit, and my early granny squares looked properly wonky for it. It’s honestly a nightmare until it isn’t.

I’ve been crocheting for a few months now, and I still sometimes have to check a conversion chart when I’m using American patterns. So don’t feel bad if you find it confusing – we all do.

This guide will explain everything about crochet hook sizes, from how they’re measured to which size you actually need for your next project. Let’s get stuck in.

How Are Crochet Hooks Measured?

Here’s the most important thing to understand: hook sizes measure the diameter of the hook’s shaft. That’s the bit between the handle and the hooked end. The thicker the shaft, the bigger the hook size.

Most modern hooks show this measurement in millimetres (mm), which is the metric system. A 4mm hook is exactly 4 millimetres thick. Simple, right? Except different countries have their own additional systems using letters and numbers, which is where it all gets complicated.

The thing is, crochet has evolved over time in different countries, and each place developed its own way of labelling hooks before anyone thought about standardising things. So now we’re stuck with multiple systems that all measure the same thing in different ways.

The Craft Yarn Council (basically the authority on yarn and hook standards) has tried to get everyone on the same page by encouraging manufacturers to prominently include millimetre sizing on packaging. But you’ll still find older hooks, vintage patterns, and American patterns that use different systems.

Understanding Different Hook Size Systems

There are three main systems you need to know about: metric sizes (used in the UK and Europe), US sizes (letters and numbers), and old UK sizes (which thankfully we don’t use much anymore but still crop up in vintage patterns).

Let me break down each one properly because this is where most people get confused.

Metric Sizes (UK and Europe)

This is what we use in the UK now, and it’s by far the easiest system. The mm size tells you exactly how thick the hook is. A 2.5mm hook is 2.5 millimetres in diameter. A 6mm hook is 6 millimetres. The bigger the number, the bigger the hook.

Common metric sizes you’ll see are:

• 2.0mm to 3.5mm – For fine work with lace-weight yarns, fingering weight, or crochet thread
• 4.0mm to 5.0mm – The most common sizes, perfect for DK yarns and worsted weight yarn
• 5.5mm to 8.0mm – For chunky yarn and bulky projects
• 10mm and above – Jumbo hooks for super chunky yarn and really quick projects

If you’re buying hooks in the UK now, they’ll almost always be labelled with metric measurements. It’s the most accurate measurement and the easiest to understand once you get used to it.

US Size System (Letters and Numbers)

American patterns use a completely different system with letters and a number combination. So you might see “H-8” or “G-6” on a hook. The letter and number together tell you the size.

The closer the letter is to A, the smaller the hook. So B is smaller than G, which is smaller than J. Makes sense so far, right? But then they also add a number, and sometimes you’ll see just the letter or just the number on older hooks.

Here’s a quick conversion of the most common US sizes:

• B-1 = 2.25mm
• C-2 = 2.75mm
• E-4 = 3.5mm
• G-6 = 4.0mm (very common size)
• H-8 = 5.0mm (another really popular one)
• I-9 = 5.5mm
• J-10 = 6.0mm
• K-10½ = 6.5mm
• L-11 = 8.0mm

If you’re following an American pattern and it says to use an H hook, you need a 5mm hook. Simple once you know the conversion.

The annoying bit is that different brands sometimes label things slightly differently, which is why the Craft Yarn Council recommends always checking the millimetre size for an accurate measurement.

Old UK Sizes

Right, this is where things get properly confusing. The old UK system (which we mostly stopped using decades ago but still appears in vintage patterns) works backwards. The smaller the number, the bigger the hook.

So a UK size 14 is actually tiny (about 2mm), whilst a UK size 4 is quite large (6mm). I know. It makes no sense.

You mainly see these on really old hooks that have been passed down, or in vintage crochet patterns from the 1950s-70s. Here’s a quick reference:

• UK 14 = 2.0mm
• UK 12 = 2.5mm
• UK 9 = 3.5mm
• UK 8 = 4.0mm
• UK 7 = 4.5mm
• UK 6 = 5.0mm
• UK 4 = 6.0mm

If you’ve inherited your nan’s old hooks and they just have a number stamped on them with no other information, this is probably what you’re dealing with. Keep a conversion chart handy because trying to remember this system is genuinely impossible.

The Crochet Hook Size Chart Everyone Needs

Here’s a conversion chart showing all three systems side by side. Bookmark this page or screenshot this table because you will need it:

Metric (mm)	US Size	Old UK Size	Yarn Weight
2.0mm	B-1	14	Lace, thread
2.25mm	B-1	13	Lace, fingering
2.5mm	–	12	Fingering
2.75mm	C-2	–	Fingering, sport
3.0mm	–	11	Sport
3.25mm	D-3	10	Sport, DK
3.5mm	E-4	9	DK
3.75mm	F-5	–	DK
4.0mm	G-6	8	DK, worsted
4.5mm	7	7	Worsted, aran
5.0mm	H-8	6	Worsted, aran
5.5mm	I-9	5	Chunky
6.0mm	J-10	4	Chunky
6.5mm	K-10½	–	Bulky
8.0mm	L-11	–	Bulky
9.0mm	M/N-13	–	Super bulky
10.0mm	N/P-15	–	Super bulky

Save this crochet hook size chart somewhere you can find it easily. I keep a printed copy in my project bag for when I’m at craft groups or working from different patterns.

This crochet hook sizes chart works for all major yarn brands available in the UK, including Red Heart, Stylecraft, King Cole, and Drops. For worsted weight yarn crochet hook size specifically, always check your yarn label first, but 5mm is the safest starting point.

Steel Crochet Hooks: A Different Beast Entirely

Right, just when you thought you’d got your head around hook sizes, steel hooks come along with their own completely different system. Because why make things simple, eh?

Steel crochet hooks are those really tiny hooks you use for fine work with crochet thread. They’re made from steel (hence the name) because they need to be strong despite being so thin. You use them for things like doilies, lace edging, and really delicate threadwork.

The confusing bit is that steel hooks have their own number system, and it works backwards compared to regular hooks. With steel hooks, the higher the number, the smaller the hook. So a size 7 steel hook is smaller than a size 1 steel hook. I know. Just when you thought you’d figured it out.

Steel crochet hook sizes typically range from 00 (the largest steel hook, about 3.5mm) down to 14 (absolutely tiny, about 0.75mm). Most people working with threads use sizes between 3 and 10.

If your pattern calls for “size 10 thread” or mentions doily-making, you’re probably going to need steel hooks. They’re completely different from regular yarn hooks, and you can’t really substitute one for the other.

Matching Hook Sizes to Yarn Weights

This is where it actually gets useful. Once you understand the sizing systems, you need to know which size hook to use with which yarn. Your yarn label will always have a recommended hook size on it, which is a brilliant starting point.

Super Fine Yarns (Lace, Fingering, Sock)

These delicate yarns need small hooks, usually between 2.0mm and 3.5mm. If you’re making lace or working with crochet thread, you might need even smaller steel hooks.

The yarn is so fine that using a bigger hook would make everything look loose and floppy. You want tight, defined stitches for this kind of work.

Light Yarns (Sport, Baby, DK)

DK yarns are brilliant and incredibly popular in the UK. They work well with hooks from 3.5mm to 4.5mm, depending on what you’re making.

A 4mm hook is probably the most common size for DK weight, and it’s what I reach for automatically when I’m starting a new DK project. It gives you neat stitches that aren’t too tight or too loose.

Medium Yarns (Worsted, Aran)

Worsted weight yarn is the standard in a lot of American patterns, and it’s similar to aran weight here in the UK. These yarns work beautifully with 4.5mm to 5.5mm hooks.

A 5mm hook (H-8 in US sizing) is the recommended hook size for most worsted-weight yarns. It’s a really comfortable size to work with and produces lovely, even stitches for things like blankets, jumpers, and bags.

If you’re specifically searching for the worsted-weight yarn crochet hook size, a 5mm (H-8) is your answer – it’s the standard recommendation across most worsted patterns in 2026.

Bulky and Super Bulky Yarns

Chunky yarn needs bigger hooks, usually 6mm to 10mm or even larger. These are brilliant for quick projects because the stitches work up so fast.

I love using a 6mm or 8mm hook with bulky yarn for making scarves and hats. You get cosy, textured fabric in hardly any time at all.

• Cosy Winter Scarf Crochet Patterns

What Hook Size Should a Beginner Crocheter Use?

If you’re just starting out, don’t go out and buy every single hook size. That would be expensive and overwhelming. Start with one or two hooks in the most common sizes and build your collection as you try different projects.

The best hook size for beginners is a 5mm (H-8). Here’s why:

It works perfectly with worsted weight yarn, which is what most beginner patterns use. You can find worsted/aran yarn everywhere; it’s not too expensive, and there are thousands of patterns designed for it.

A 5mm hook is comfortable to hold. It’s not so small that you’re squinting at tiny stitches, but not so big that it feels awkward in your hand. It’s the Goldilocks of hook sizes – just right.

Most standard crochet hooks in beginner sets include this size. If you buy a multi-pack (which is often good value), you’ll definitely get a 5mm hook included.

Once you’re comfortable with a 5mm hook, add a 4mm and a 6mm to your collection. Those three sizes will probably cover 80% of the projects you’ll want to make as you’re learning.

Some ideal beginner crochet projects:

• Crochet Valentine’s Gifts
• Easter Crochet Projects

2026 Update on Beginner Hook Recommendations: The 5mm hook remains the gold standard for beginners. Most crochet starter kits sold in 2026 include this size alongside 4mm and 6mm options, giving you the perfect range to tackle any beginner pattern using worsted weight or aran yarn.

Different Types of Hook Materials

The size isn’t the only thing that matters – the material your hook is made from affects how it feels to use. Different hook materials suit different people and different projects.

Aluminum Hooks (or Aluminium if You’re British)

These are the standard. Most crochet hooks are made from smooth aluminum because it’s lightweight, durable, and slides through yarn easily. The smooth aluminum surface means your yarn doesn’t catch or snag.

Ergonomic Crochet Hooks

These have chunky, padded handles designed to reduce hand strain. If you’re planning long crochet sessions or have any issues with your hands, wrists, or arthritis, ergonomic crochet hooks are brilliant.

They’re more expensive than basic aluminum hooks, but they’re worth it if you find standard hooks uncomfortable. Brands like Clover and Prym make excellent ergonomic ranges with soft-touch grips. I use these most of the time. 

Wooden Hooks

Wooden hooks feel lovely and warm in your hand, and some people prefer the slightly rougher surface because it gives you more control over your yarn. They’re perfect for slippery yarns that might slide off metal hooks.

The downside is they can be more expensive and aren’t available in as many sizes. They’re also more fragile than metal. I use these in bigger sizes as my ergonmic hooks only go up to 6mm, and I got some wooden ones with my yarn bowl. 

Plastic Hooks

Cheap and cheerful, plastic hooks are what you often get in beginner sets. They’re fine for learning, but they’re not as durable as metal and can sometimes catch on yarn.

That said, some people love plastic hooks because they’re incredibly lightweight. If metal hooks feel too cold or heavy, plastic might work better for you.

What about left-handed crocheters?

Quick aside because it took me ages to figure this out. I’m left-handed, but I crochet right-handed — it just felt more natural, and most patterns and tutorials assume you’ll work right-handed. You don’t need special left-handed hooks unless you’re crocheting in your left hand, in which case Clover does make a small range. But honestly, most left-handed crocheters I’ve come across just learned right-handed and got on with it. Worth trying both before you commit to a side.

Inline Hooks vs Tapered Hooks

This is less about material and more about shape. Inline hooks have a deeper throat and create more consistent stitches. Tapered hooks have a shallower throat and some people find them easier to insert into tight spaces.

There’s no right answer here – it’s entirely personal preference. I use both depending on what I’m making.

How to Tell What Size Your Hook Is

Sometimes you’ve got a hook with no markings, or the writing has worn off, or you’ve inherited a box of random hooks from a car boot sale. How do you tell what size they are?

The best way is to use a crochet hook gauge. It’s a little tool (usually plastic or metal) with holes in it ranging from 2mm to 10mm. You stick your hook through the holes until you find one that fits snugly, and that tells you the size.

You can buy hook gauges really cheaply online or from any decent craft shop — Hobbycraft, Wool Warehouse, or even The Range usually have them. They’re honestly worth having because guessing hook sizes by eye is basically impossible – the difference between a 4mm and 4.5mm hook is tiny.

If you haven’t got a gauge, check if your hook has any markings at all – letters, numbers, anything. Then use a conversion chart to figure out what it is. Old hooks might only have a UK size number, whilst American hooks might just have a letter.

Understanding Gauge and Why It Matters

Right, this bit is important, but also the bit everyone wants to skip. I get it – making a gauge swatch feels boring when you just want to start your actual project. But trust me, it matters.

Gauge (or tension, as some patterns call it) is how many stitches and rows you get per 10cm square using a specific hook and yarn. The pattern will tell you what gauge you need to achieve – something like “20 stitches and 24 rows = 10cm using 4mm hook.”

If your gauge doesn’t match the pattern, your finished project will be the wrong size. This is fine for things like scarves or blankets, where exact size doesn’t matter much. But for garments, bags, or anything that needs to fit properly, getting the gauge right is crucial.

To make a gauge swatch:

1. Make a small square (usually 15cm x 15cm) using the recommended hook size and the yarn you’re planning to use
2. Measure how many stitches you get across 10cm in the middle of your swatch
3. Count how many rows you get over 10cm vertically
4. Compare your numbers to the pattern gauge information

If your swatch is larger than the pattern gauge (fewer stitches per 10cm), you need a smaller hook size. If it’s smaller (more stitches per 10cm), you need a bigger hook.

Even a half a millimetre difference in hook size can affect your gauge significantly. That’s why patterns are specific about hook sizes – they’ve worked out exactly what size gives them the best results for that particular design.

When to Use a Different Hook Size Than Recommended

Sometimes you deliberately want to use a different hook size than what the pattern or yarn label suggests. Here are the main reasons you might do this:

To match gauge – This is the most common reason. If your natural tension is tighter or looser than the pattern designer’s, you’ll need to adjust your hook size to match their gauge.

For a different fabric texture – Using a larger hook size with the same yarn creates a looser, more drapey fabric. Using a smaller hook creates tighter, denser fabric. You might want this for specific effects.

For amigurumi and toys – Most amigurumi patterns tell you to use a smaller hook than the yarn label recommends. This creates really tight stitches so the stuffing doesn’t show through.

For lacework – Lacy, open patterns often use a much larger hook than you’d normally pair with that yarn weight to create those beautiful open spaces.

The right crochet hook size for your project depends on what you’re making and what effect you want. Don’t be afraid to experiment – that’s how you learn what works.

Building Your Hook Collection

You don’t need to buy all the crochet hook sizes at once. Start small when you are learning to crochet and add to your collection as you need different sizes. Here’s what I’d recommend:

Essential starter sizes:

• 4mm (for DK yarns)
• 5mm (for worsted/aran – the most versatile)
• 6mm (for chunky yarn)

These three will cover most beginner and intermediate patterns.

Next additions:

• 3.5mm (for finer DK and sport weight)
• 7mm or 8mm (for bulkier projects)
• 2.5mm or 3mm (if you want to try finer work)

Eventually, if you get really into crochet:

• A range of steel hooks for thread work
• Tunisian crochet hooks (long hooks with a stopper on the end)
• Jumbo hooks (10mm+) for super quick chunky projects
• A nice set of ergonomic hooks if you’re crocheting a lot

You can buy hooks individually or in sets. Sets are often a better value if you know you’ll use multiple sizes. I started with a cheap crochet starter kit from Amazon that had 10 different sizes (plus some yarn and accessories), and it was brilliant for figuring out which sizes I actually used most.

Keep your hooks in a proper case or project bag so you don’t lose them. I’ve lost so many hooks down the back of the sofa or in the bottom of my handbag. A dedicated case keeps them all together and makes it easy to see which sizes you have.

Reading Your Yarn Label

Your yarn label is honestly your best friend when you’re trying to work out what size hook to use. Every ball of yarn has a band wrapped around it with loads of useful information, including the recommended hook size.

Look for the little symbol that looks like a crochet hook. Next to it, you’ll see a number – that’s the millimetre size the yarn manufacturer recommends. It’s usually a good starting point, though remember it’s a suggestion rather than a rule.

The yarn label will also tell you:

• The yarn weight (lace, fingering, DK, aran, chunky, etc.)
• The fibre content
• How much yarn is in the ball (very important for calculating how much you need)
• Washing instructions
• The dye lot number (if you’re buying multiple balls, make sure they’re all the same dye lot or the colours might not match exactly)

Different brands of the same yarn weight might suggest slightly different hook sizes. That’s because the specific yarn – how it’s spun, what it’s made from, how thick the individual strands are – affects what hook works best with it.

When you’re substituting one yarn for another in a pattern, check that the recommended hook sizes are similar. If the pattern uses a yarn that suggests 4mm and you’re replacing it with yarn that suggests 5mm, you’ll need to adjust accordingly or your finished piece will be a different size.

Common Questions About Hook Sizes

Can I use a bigger hook with thin yarn?

Yes, but your fabric will be very open and lacy. This can be lovely for summer shawls or light wraps, but it won’t work for things that need structure like bags or toys.

What if I can’t find the exact hook size the pattern calls for?

Going up or down by 0.25-0.5mm usually won’t make a massive difference, especially for projects where the exact size doesn’t matter. Just make your gauge swatch to check.

Why do my stitches look different to the pattern photo?

Could be hook size, could be yarn, could be your personal tension. Everyone crochets slightly differently. As long as your gauge matches and you’re happy with how it looks, you’re fine.

Do expensive hooks make a difference?

Sort of. Cheap hooks work fine, but really good quality hooks glide through yarn more smoothly, are more comfortable for long sessions, and last longer. Whether that’s worth the extra money is up to you.

How many hooks do I actually need?

Start with 2-3 in the most common sizes. Add more as you try different projects. You definitely don’t need every single size.

Tips for Getting Started

Here’s what I wish someone had told me when I was learning about hook sizes:

Don’t overthink it. Yes, hook size matters, but if you’re off by half a millimetre, it’s not the end of the world. Make your gauge swatch, check it matches the pattern, and crack on.

Trust your yarn label. It’s there for a reason. The recommended hook size is a good starting point.

Your tension will change as you improve. When you first start crocheting, your tension is usually quite tight because you’re tense and concentrating hard. As you relax and get more confident, your stitches will naturally loosen up. This means you might need to adjust hook sizes as you get better.

Save your gauge swatches. I keep all mine in a box with notes about what yarn, what hook, what pattern. It’s really useful reference for future projects.

Buy a hook gauge. Seriously, they’re about £3 and save so much hassle.

Start with mid-range sizes. Don’t begin your crochet journey trying to make lace doilies with 0.75mm steel hooks. Start with worsted weight yarn and a 5mm hook. You’ll have much more success and actually enjoy it.

My actual hook collection (and what I reach for most)

Real talk: I have far more hooks than I need, and there are about three sizes I actually use most weeks.

• 5mm — my most-used hook by a country mile. Worsted weight, granny squares, hats, the lot. If I had to keep one hook only, this is it.
• 4mm — for DK yarn, which is what I tend to buy when I want something more delicate. Most of my cardigan-pattern attempts have used this.
• 9mm wooden hook — for chunky yarn. I got this with a yarn bowl set, and it’s still my go-to for quick scarf or chunky cardigan projects.
• My ergonomic Clover set (2.25mm to 6mm) — what I use for long sessions. The chunky soft handles really do make a difference if you’re crocheting for hours.
• The starter-kit aluminium hooks — still in the project bag for when I lose the proper ones (often). Don’t underestimate a cheap basic set.

The sizes I almost never reach for: anything under 3mm (I haven’t done thread work yet), and anything bigger than 10mm (haven’t gone full jumbo blanket yet). That’ll probably change once I run out of project ideas in the middle range.

Final Thoughts

I know this has been a massive info dump about hook sizes, but honestly, once you’ve been crocheting for a bit, it all becomes second nature. You’ll automatically reach for the right size hook for your yarn without really thinking about it.

The key things to remember are:

• Metric (mm) sizing is the most accurate measurement
• Your yarn label suggests the best hook size for that specific yarn
• Making a gauge swatch is boring but important for fitted projects
• It’s okay to experiment with different hook sizes for different effects
• Start with common sizes (4mm, 5mm, 6mm) and build from there

Don’t let hook sizing confusion put you off crochet. Once you’ve got your head around the basics, it’s honestly fine. And there are loads of conversion charts online (including this one!) to help when you’re stuck.

The most important thing is to just pick up a hook and start making something. You’ll learn way more from actually crocheting than from reading about it. Though obviously reading about it helps too, which is why you’re here!

Right, I’m off to start a new blanket. I’ve got some gorgeous chunky yarn that’s been sitting in my stash for ages, and I reckon a 6mm hook will be perfect. See, you’ll be making these decisions without thinking about it soon, too.

Happy crocheting!

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