Knitting Needle Size Converter
Knitting needle sizes are expressed in three different systems: US sizes (numbers that increase with needle diameter), old UK and Canadian sizes (numbers that decrease with needle diameter), and metric millimetre sizes (the international standard). Converting between them is essential when following patterns from different countries or working with needles that are only labelled in one system. A US size 8 is not the same as a UK size 8 (they are very different diameters), and this confusion trips up many knitters switching between patterns. This converter uses the complete standard Craft Yarn Council reference table to look up any size in any system and instantly show the equivalents in the other two systems. The complete reference table is also shown below so you can browse all sizes at a glance. Metric mm sizes are the only unambiguous international standard and should always be your primary reference when selecting needles for a pattern.
US -- = -- mm = UK --
How the converter works
The converter uses a lookup table of all standard needle sizes from the Craft Yarn Council. Select which system your needle is labelled in, choose the size, and the converter instantly shows the equivalent sizes in the other two systems. Where no equivalent exists in the UK scale, the table shows "--".
Note that US size 1.5 (2.5 mm) shares the UK 12 designation with US size 2 (2.75 mm) in some references; the Craft Yarn Council table lists both. Always confirm the metric mm size on your needle when in doubt.
Complete knitting needle size reference table
All standard sizes per the Craft Yarn Council knitting gauge standards.
| US Size | Metric (mm) | UK / Canadian |
|---|---|---|
| US 0 | 2 mm | UK 14 |
| US 1 | 2.25 mm | UK 13 |
| US 1.5 | 2.5 mm | UK 12 |
| US 2 | 2.75 mm | UK 12 |
| US 2.5 | 3 mm | UK 11 |
| US 3 | 3.25 mm | UK 10 |
| US 4 | 3.5 mm | No equivalent |
| US 5 | 3.75 mm | UK 9 |
| US 6 | 4 mm | UK 8 |
| US 7 | 4.5 mm | UK 7 |
| US 8 | 5 mm | UK 6 |
| US 9 | 5.5 mm | UK 5 |
| US 10 | 6 mm | UK 4 |
| US 10.5 | 6.5 mm | UK 3 |
| US 11 | 8 mm | UK 0 |
| US 13 | 9 mm | UK 00 |
| US 15 | 10 mm | UK 000 |
| US 17 | 12 mm | No equivalent |
| US 19 | 15 mm | No equivalent |
| US 35 | 19 mm | No equivalent |
| US 50 | 25 mm | No equivalent |
Notes on the UK sizing system
The old UK and Canadian sizing system is now largely obsolete. Modern UK needles are labelled in metric mm, matching the international standard. The old system is still relevant for vintage patterns published before the 1970s. In the old UK system, the numbers run in reverse order: the smallest number (UK 000) is the largest needle (10.0 mm), and the largest number (UK 14) is the smallest needle (2.0 mm). This is the opposite of the US system.
Some US sizes have no old UK equivalent (shown as "No equivalent" in the table above). In those cases, the metric mm size is the only reliable cross-reference.
Frequently asked questions
Why do US and UK needle size numbers go in opposite directions?
US needle sizes increase as the needle gets larger: US 0 is 2.0 mm and US 50 is 25.0 mm. UK and Canadian old needle sizes work the opposite way: larger numbers mean finer (smaller) needles. UK size 14 is 2.0 mm (the finest) and UK size 000 is 10.0 mm. This reversal confuses many knitters, especially when following vintage UK patterns on modern US needles. Always check the metric (mm) size, which is the unambiguous international standard.
Which needle sizing system should I use?
The Craft Yarn Council and most modern yarn labels recommend using metric (mm) sizes as the primary reference because they are internationally consistent and unambiguous. US sizes are still widely used in North American patterns. UK sizes in current use (post-1970s) have mostly been replaced by metric on modern UK needles. For vintage British or Canadian patterns, the old UK size numbers apply.
Why are some US sizes missing from the UK column?
Not every US size has a direct UK equivalent. For example, US 4 (3.5 mm) has no UK size assignment in the traditional UK scale, and US 11 skips to 8.0 mm while UK sizes jump from 1 to 0. The UK sizing system was not perfectly aligned with the metric or US scales, leaving some gaps. When a UK equivalent does not exist, the metric size is the only reliable cross-reference.
What is the difference between single-point, double-point, and circular needles?
The diameter (size) is the same regardless of needle type. Single-point needles are straight with a point at one end. Double-point needles have points at both ends and are used for knitting in the round on small circumferences such as socks. Circular needles have two short tips connected by a flexible cable and are used for both flat and in-the-round knitting. All three types use the same size numbering systems.
My needles are not marked. How can I find the size?
Use a knitting needle gauge, a small plate with holes of precise diameters. Slide the needle into holes until it fits snugly without force; the label on that hole gives the metric mm size. You can then use this converter to find the US or old UK equivalent. Needle gauges are widely available and inexpensive at yarn and craft stores.
Official sources
- Craft Yarn Council knitting gauge standards: www.craftyarncouncil.com/standards/knit-gauge.
- Craft Yarn Council standard needle and hook sizes table (all US, metric, and UK equivalents as published by the industry body).
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.