No bones about it, crochet hook sizes are confusing. Should you follow the letter, the number, or the millimeter when selecting a crochet hook for your next project? This article, including a handy crochet hook conversion chart, will help!
Crochet Hook Sizes & Conversion Chart
There are several different ways in which hook sizes can be labeled. With so many variations, crocheters are bound to get confused at some point along the journey. Which sizing method is tried and true? First let’s discuss all of the ways crochet hooks are categorized and sized.
Crochet hooks can be made using a variety of materials including wood, aluminum, plastic, and bamboo, among others. The majority of hooks range from 5″ in length (such as the Clover Soft Touch) to 6″ (such as Susan Bates, Radiant, and Boye), to 7″ (such as the Furls Streamline Swirl).
Different hook manufacturers label their hook sizes using different methods. Some hook brands use the American letter system, some use the American number system (which is not the same as the metric number), some use both of these, and then others only use the actual width of the shaft in millimeters. Because it is up to each individual crochet hook manufacturer to label their hooks, the best way to determine hook size is to go by the actual measurement: that is, the size in millimeters. This is quite literally the width of the shaft of the crochet hook.
The American system of labeling crochet hooks uses the alphabet. Starting with a B (2.25mm) and ranging up to an S (19mm), although M/N is typically as large as you’ll need in your arsenal.
The UK method of sizing crochet hooks uses numbers. The smaller the number, the larger the hook. Confusing? I know.
Because of how muddy these waters can be, there is one characteristic that ALL crochet hook sizes have: the actual measurement of the shaft. If the size in millimeters is not listed on your hook, a hook gauge is an excellent tool to have in your crochet kit. Note that there are gauge tools for both knitting and crochet – and they are not necessarily interchangeable.
In order to correctly check the size of crochet hooks you want to get the kind that has a slot into which you rest the hook, NOT a hole that you put the hook through (like this one).
The holes are better used for knitting needles, since the head of the crochet hook can be funkily shaped depending on the brand and may not give an accurate reading. The hook shaft should fit perfectly when slid into the corresponding slot.
The bottom line is that the best means of selecting a hook size will always be to go off of the millimeter itself. For example, the diameter of a 6mm crochet hook (also known as a size J/10 in American terms or size 4 in UK terms) is just that: 6 millimeters. It doesn’t matter which brand, where it was produced, how long the hook itself is. If the width of the hook is 6mm, it is universally known as a 6mm hook.
The Furls Streamline Swirl G+, 4.5mm hook.
To further add to the confusion, not all hook sizes have the equivalent depending on which terms you use. For example, a size 4.5mm hook has no real American letter size (although some call it a G+), and is commonly referred to as a size 7 in both the US and the UK. Not to be confused with a 7mm hook, which does not have an American letter OR a UK number. Oy!
The Clover Amour hooks are my favorite for “larger” hook sizes and range from 6.5mm to 15mm.
Save this handy Crochet Hook Size Conversion Chart for future reference.
One last note about crochet hook sizes. You may have seen some tiny, tiny hooks. Those are used for making doilies etc, and are a whole different ballgame. Those steel hooks are for crocheting with crochet thread… but going by millimeter will always your best bet there as well.
Have questions? Feel free to ask in the Heart Hook Home Crochet Community where there are over 65,000 other friendly crocheters! Happy crocheting!