Crochet hook size chart: millimeters to US letters and numbers

Crochet hook sizes: millimeters and US sizes

The millimeter size is the hook measured across its shaft. Go by it: US letters and numbers are names, and makers do not all use them the same way.
Some letters are listed at two or three sizes: D, G, N, P, Q, T and X. A pattern that says only "P hook" may mean 10 mm, 11.5 mm or 15 mm. If your pattern gives only a letter, look for the millimeters in it, and check the millimeters on your own hook.
2.5 mm and 7 mm have no US size in the charts we read.
The chart of hooks by yarn weight writes two of these sizes more shortly: M/N-13 (9 mm) as M-13 and P/Q (15 mm) as Q.
Every size here is in two or more of the charts we read. 3 sizes that only one chart gives are left out, and so are steel hooks for crochet thread and the old United Kingdom numbers.

Go by the millimeters marked on the hook or its package. The US letter and number differ from maker to maker.
The right hook is the one that gives your pattern's gauge. Make a swatch: if it comes out larger than the pattern says, try a smaller hook; if it comes out smaller, try a larger one.
Steel hooks, used for crochet thread and lace yarn, are numbered the other way round: the higher the number, the smaller the hook.

What size is an H hook in millimeters?: H-8 is 5 mm.
What US size is a 4 mm hook?: G-6. Some makers sell a 4.25 mm hook as G, so check the millimeters on yours.
What is a 3.5 mm hook in US sizes?: E-4.
What size is a J hook?: J-10 is 6 mm.
What size is a P hook?: It depends on the maker: P is listed at 10 mm (N/P-15), 11.5 mm (P-16) and 15 mm (P/Q). Go by the millimeters.

Why does my hook have a letter, a number and millimeters?: Hooks sold in the United States carry a letter, a number or both, and the size in millimeters. The millimeters are the measurement; the letter and number are names for it.
Is a higher number a bigger hook?: For regular hooks, yes: the letters and numbers rise with the millimeters. Steel hooks for thread run the other way.
What are the smallest and the largest crochet hook sizes?: On this chart the smallest hook is 2.25 mm (B-1) and the largest is 30 mm (T/X). Steel hooks, used for crochet thread and lace yarn, go smaller still: the steel hook chart lists them.
How do I find the size of a hook with no marking?: A hook's size is the width of its shaft. A hook gauge is a card with a row of sized holes: find the hole the shaft fits and read its millimeters.

Abbreviations What does this abbreviation in my pattern mean?
US and UK terms What does this stitch name mean in US terms and in UK terms?
Chart symbols What does this symbol on a crochet chart mean?
Japanese chart symbols What does this symbol on a Japanese chart mean?
Terms in other languages What is this stitch called in a pattern written in another language?
Hook size for your yarn weight Which hook do I use with this yarn?
Hook size by project What size hook do I use for the thing I am making?
Steel hook sizes What size is my steel crochet hook in millimeters?
Knitting needle to hook size Which crochet hook is the same size as my knitting needle?
Yarn weight chart What weight is my yarn, and what else is it called?
Thread size chart How thick is this size of crochet thread?
Starting chain calculator How many chains do I start with for this width?
Yarn calculator How much yarn do I need to finish this?
Blanket size chart How big should I make this blanket?
Baby blanket size chart How big should I make a baby blanket?
Scarf size chart How long and how wide do I make a scarf?
Hat size chart How big is the head I am making this hat for?
Size chart for babies How big are a baby's head and feet at this age?
Headband size chart How long do I make a headband or an ear warmer?
Slipper size chart How long is the foot for this shoe size?
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