Crochet Hook Size Chart

Use this crochet hook size chart to compare US, UK and metric sizes, choose the right hook for your yarn, and fix common gauge problems.

CROCHET PATTERNSDIY IDEAS

9/9/20269 min read

Crochet Hook Size Chart: US, UK & Metric Guide

Choosing a crochet hook should be simple, but different sizing systems can make it surprisingly confusing. A pattern might recommend a US H-8 hook, while your hook set is labeled 5.0 mm. Another older pattern may call for a UK 6 hook, leaving you wondering whether you have the right tool.

The good news is that crochet hook sizes can be compared once you understand how the labeling systems work.

This crochet hook size chart explains the commonly encountered US, UK, and metric crochet hook sizes, how hook measurements relate to yarn, why gauge matters, and what to do when your pattern and hook collection use different sizing systems.

Crochet Hook Size Chart: US, UK, and Metric

The metric measurement refers to the diameter of the hook shaft in millimeters. US and UK labeling systems use letters or numbers and don't always follow a simple mathematical progression.

Here are commonly encountered conversions:

Metric US Size UK Size

2.0 mm — 14

2.25 mm B/1 13

2.5 mm C/2 12

2.75 mm C/2 —

3.0 mm — 11

3.25 mm D/3 10

3.5 mm E/4 9

3.75 mm F/5 —

4.0 mm G/6 8

4.5 mm 7 7

5.0 mm H/8 6

5.5 mm I/9 5

6.0 mm J/10 4

6.5 mm K/10.5 3

7.0 mm — 2

8.0 mm L/11 0

9.0 mm M/N/13 —

10.0 mm N/P/15 —

12.0 mm O/16 —

15.0 mm P/Q —

16.0 mm Q —

19.0 mm S —

Important: Hook labeling can vary between manufacturers, especially for larger hooks and hooks near the boundaries between traditional sizing systems. When a metric measurement is printed on the hook, use the millimeter size as your primary reference.

What Does the Millimeter Size Mean?

The metric size tells you the approximate diameter of the hook shaft.

For example:

  • A 3.5 mm hook has a smaller shaft than a 5.0 mm hook.

  • A 6.0 mm hook is larger than a 4.0 mm hook.

  • A larger hook generally creates larger stitches when used with the same yarn and technique.

The metric measurement is especially useful because it gives you a physical measurement rather than relying on a letter or number that can vary between sizing systems.

If you are buying a crochet hook set, a set containing clearly marked millimeter sizes can make it easier to match hooks to patterns.

US Crochet Hook Sizes Explained

US crochet hooks are commonly identified using letters, numbers, or both.

For example:

  • B-1 = approximately 2.25 mm

  • C-2 = approximately 2.5 mm

  • D-3 = approximately 3.25 mm

  • G-6 = approximately 4.0 mm

  • H-8 = approximately 5.0 mm

  • I-9 = approximately 5.5 mm

  • J-10 = approximately 6.0 mm

  • K-10.5 = approximately 6.5 mm

You may see a pattern written as H-8, H/8, or simply H.

These references generally point to the same commonly used US hook size, but the safest way to confirm the actual hook is to check its millimeter measurement.

Why US Labels Can Be Confusing

US hook numbering does not simply increase in a perfectly predictable mathematical sequence.

For example, a hook labeled H-8 is 5.0 mm, while an I-9 is 5.5 mm. But not every possible letter-number combination is used consistently across the entire range.

That's one reason experienced crocheters often pay more attention to the metric measurement.

UK Crochet Hook Sizes Explained

Older crochet patterns and some publications may use UK hook numbers.

This can be confusing because the numbering moves in the opposite direction from what you might expect when comparing it with metric sizes.

For example:

  • UK 14 is approximately 2.0 mm

  • UK 10 is approximately 3.25 mm

  • UK 8 is approximately 4.0 mm

  • UK 6 is approximately 5.0 mm

  • UK 5 is approximately 5.5 mm

  • UK 4 is approximately 6.0 mm

  • UK 3 is approximately 6.5 mm

  • UK 2 is approximately 7.0 mm

So a smaller UK number does not necessarily mean a smaller hook.

When converting an older UK pattern, don't guess based on the number alone. Find the metric equivalent and check the gauge instructions in the pattern.

Why Crochet Hook Size Matters

Your crochet hook affects the size, density, texture, and drape of your stitches.

Using a smaller hook with the same yarn will generally produce a tighter fabric. A larger hook will generally produce a looser fabric.

That difference can affect:

  • Finished dimensions

  • Stitch definition

  • Fabric drape

  • Firmness

  • Yarn consumption

  • The amount of stretch

  • Overall appearance

Imagine a blanket pattern that is designed to finish at a particular width. If your stitches are substantially smaller than the designer's gauge, your finished blanket may be narrower than expected.

The opposite can happen if your stitches are too loose.

This is why choosing a hook isn't simply about matching the yarn label.


How to Choose the Right Crochet Hook

Start with the pattern whenever you are following a specific crochet design.

If the pattern recommends a 5.0 mm hook, look for a hook that actually measures 5.0 mm, even if your hook set uses a different labeling system.

Step 1: Check the Pattern

Look for the recommended hook size and gauge information.

A pattern may say something like:

Hook: 5.0 mm (US H-8)

If your hooks are marked only in metric sizes, choose the 5.0 mm hook.

Step 2: Check Your Yarn

The yarn label often provides a suggested hook range.

Treat this as a starting point rather than an absolute rule.

The appropriate hook can change depending on what you are making.

For example, a crocheted basket may need a firmer fabric, while a lightweight garment may benefit from more drape.

Step 3: Make a Gauge Swatch

If the finished size matters, make a gauge swatch before beginning the project.

Crochet a sample using the yarn, stitch pattern, and hook you plan to use.

Measure the number of stitches and rows over the specified area.

If you have too many stitches in the measured area, your stitches are smaller than the target gauge. Try a larger hook.

If you have too few stitches, your stitches are larger than the target gauge. Try a smaller hook.

What If You Don't Have the Exact Hook Size?

Don't automatically abandon a project because you are missing the recommended hook.

First, check whether you have a nearby metric size.

For example, if a pattern recommends 5.0 mm and you only have 4.5 mm and 5.5 mm hooks, either may be worth testing with a gauge swatch.

However, the result is not guaranteed to match the pattern.

Your yarn, tension, stitch pattern, and crochet technique all affect gauge.

For a project where exact measurements are important, make the swatch and choose the hook that gives you the required gauge.

Crochet Hook Size and Yarn Weight

Hook size and yarn weight work together.

A very small hook paired with bulky yarn can produce a dense fabric that may be difficult to work. A very large hook paired with fine yarn can create a much more open fabric.

Common yarn categories include:

  • Lace

  • Super Fine

  • Fine

  • Light

  • Medium

  • Bulky

  • Super Bulky

  • Jumbo

Each category can cover a range of yarn constructions and thicknesses, so the yarn label's suggested hook range can be useful.

But your project's purpose matters too.

For Blankets

You may want a hook that produces comfortable stitch definition while maintaining the amount of drape you want.

For Bags and Baskets

A smaller hook can sometimes help create a firmer fabric, depending on the yarn and stitch pattern.

For Garments

Gauge and fabric drape are especially important. The hook that works for a blanket made from the same yarn may not produce the fabric you want for a sweater.

For Amigurumi

A relatively tight fabric is often desirable so stuffing does not easily show through the stitches. The appropriate hook depends on the yarn and the desired finished fabric.

Understanding Crochet Hook Size and Gauge

Gauge is one of the most important reasons not to choose a hook based solely on a conversion chart.

Suppose a pattern requires:

16 stitches = 4 inches

That means the target stitch gauge is:

16 ÷ 4 = 4 stitches per inch

If you want an approximately 18-inch-wide piece, a basic estimate would be:

18 × 4 = 72 stitches

However, that 72-stitch estimate is only a starting point.

You may need to adjust it for the pattern's stitch multiple, border, shaping, or construction method.

Your personal tension can also change the result.

This is why the hook size printed in a pattern is not always the final answer. The gauge is the result you need to reproduce.

What to Do When Your Gauge Is Wrong

Your Gauge Is Too Tight

If you are getting more stitches per inch than the pattern specifies, your stitches are smaller.

Try moving to a larger hook.

For example, you might test a 5.5 mm hook instead of a 5.0 mm hook.

Your Gauge Is Too Loose

If you are getting fewer stitches per inch than the pattern specifies, your stitches are larger.

Try a smaller hook.

For example, you might test a 4.5 mm hook instead of a 5.0 mm hook.

Your Stitch Gauge Is Right but Row Gauge Is Wrong

This situation can happen.

If the pattern gives both stitch and row gauge, compare both measurements.

Depending on the construction of the project, row height may affect the finished dimensions, shaping, or placement of design elements.

Don't automatically change hook size without considering what part of the gauge is most important for the project.

US vs. UK vs. Metric: Which System Should You Use?

If you have a choice, metric millimeter sizing is often the easiest reference point.

That's because the measurement directly describes the hook diameter.

For example, if two patterns use different labeling systems but both specify a 5.0 mm hook, you know they are referring to the same metric diameter even if one calls it US H-8 and another gives a different regional designation.

When reading a pattern, it is useful to record all available information:

5.0 mm — US H-8

That gives you both the metric and US references.

Common Crochet Hook Sizing Mistakes

Mistake 1: Assuming Letter Sizes Increase Perfectly

US letter sizes aren't a perfectly continuous sequence.

Check the actual millimeter size instead.

Mistake 2: Treating a Conversion Chart as a Guarantee

A conversion chart helps you identify approximately equivalent hook labels. It does not guarantee that a different hook will produce the same gauge.

Mistake 3: Ignoring Gauge

For fitted garments and projects with specific finished dimensions, skipping the gauge swatch can create unnecessary problems later.

Mistake 4: Choosing Only by Yarn Label

The yarn manufacturer's suggested hook range is useful, but the project may require a different fabric density.

Mistake 5: Forgetting Crochet Tension

Two crocheters can use the same yarn and hook and still produce different gauges.

Your hands matter too.

How to Organize Your Crochet Hooks

A simple organization system can save time when you have multiple hook sets.

Consider storing hooks in metric order:

2.0 → 2.25 → 2.5 → 2.75 → 3.0 → 3.25 → 3.5 → 3.75 → 4.0 → 4.5 → 5.0 → 5.5 → 6.0 mm

Continue with larger sizes as needed.

This makes it easy to find a replacement when a pattern uses a different regional sizing system.

If your hooks have multiple labels, write the metric size on your storage case or use a small organizer with clearly marked compartments.

A Simple Rule for Choosing Your Hook

When you're unsure which crochet hook to use, follow this order:

  1. Check the pattern's recommended hook.

  2. Convert the size to millimeters if necessary.

  3. Check the yarn label for its suggested range.

  4. Consider the fabric you want.

  5. Make a gauge swatch when size matters.

  6. Adjust the hook size based on your gauge.

This approach is more reliable than choosing a hook simply because it is the size traditionally associated with a particular yarn weight.

Final Thoughts

A crochet hook size chart is useful for decoding patterns, especially when you work with designs from different countries or older publications.

The most important number to remember is the metric measurement in millimeters. US and UK labels can help you recognize a hook, but metric sizing provides a straightforward way to compare the physical diameter.

Most importantly, don't let the recommended hook size replace your own gauge test when the finished measurements matter.

Once you understand the relationship between hook size, yarn, tension, and gauge, choosing the right crochet hook becomes much easier—and you can confidently work with patterns regardless of which sizing system they use.

FAQ

What is a 5 mm crochet hook in US size?

A 5.0 mm crochet hook is commonly labeled US H-8.

What is a 4 mm crochet hook in US size?

A 4.0 mm crochet hook is commonly labeled US G-6.

What is a 6 mm crochet hook in US size?

A 6.0 mm crochet hook is commonly labeled US J-10.

Are UK and US crochet hook sizes the same?

No. US and UK systems use different labeling conventions. A UK hook number should not be assumed to correspond directly to the same US number. When in doubt, use the metric millimeter measurement.

Should I always use the hook size recommended on the yarn label?

Not necessarily. The yarn label provides a useful starting point, but the best hook depends on the project, stitch pattern, desired fabric, and your personal tension.

Why is my crochet project coming out too small?

Your stitches may be tighter than the pattern's gauge. Try making a gauge swatch and, if necessary, testing a larger hook to produce larger stitches.