Hook & Needle Size Converter
Switch between US, UK/Canada, and metric sizing instantly, for both crochet hooks and knitting needles, with a full reference chart.
Circle size compares this to the other sizes on the chart below — bigger circle, bigger hook or needle.
Full crochet hook chart
| Metric | US | UK / Canada |
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About this hook & needle size converter
Crochet hooks and knitting needles are sized differently depending on where a pattern was written — US patterns typically use a letter-and-number system (like G-6 or US 8), UK and Canadian patterns use their own numbering that often runs in the opposite direction, and metric millimeter sizing is used almost everywhere as the underlying, unambiguous measurement. This tool converts between all three instantly, for both crochet hooks and knitting needles, so a pattern written in one system doesn't leave you guessing which hook or needle you actually own.
Pick whichever system you already know your size in, choose your exact size from the list, and the other two systems update immediately, along with a relative-size visual showing roughly how big that hook or needle is compared to the rest of the range. The full reference chart below highlights your current selection, so you can see it in context alongside every other standard size.
Not every size lines up neatly across all three systems — UK sizing in particular skips some sizes that exist in the US/metric range, and vice versa. Where there's no exact match in a given system, this tool says so plainly rather than guessing or rounding to a nearby size that isn't actually correct.
Millimeter size is genuinely the most reliable of the three to shop or swap by, since it's a physical measurement rather than a naming convention that varies by brand or region — when in doubt, or when buying from a brand you haven't used before, matching the millimeter size is the safest bet.
Sizing follows the standard chart used by most yarn and pattern brands, though a few brands vary slightly from it. Nothing you select here is uploaded anywhere; the conversion happens entirely in your browser.
Frequently asked questions
Why don't US, UK, and metric sizes always have exact matches?
The three systems weren't designed to align perfectly with each other. UK/Canada sizing in particular has gaps relative to the US/metric range. Where there's no exact equivalent, this tool says so rather than rounding to something incorrect.
Which system should I trust most when buying a new hook or needle?
Millimeter size, since it's an actual physical measurement rather than a naming convention that can vary slightly by brand. If a brand's US or UK label ever seems off, the mm size is the more reliable reference.
Does this cover both crochet hooks and knitting needles?
Yes, use the "Crochet Hooks" / "Knitting Needles" toggle at the top to switch between the two separate size charts.
What does the size circle actually show?
A rough visual comparison of your selected size against the full range covered by the chart below it — a quick way to see whether you're working with a fine, mid-range, or large hook or needle at a glance.
Is my selection saved or uploaded anywhere?
No. Everything happens locally in your browser; nothing is sent anywhere.