How to Convert Old UK Knitting Needle Sizes to Metric & US

To convert old UK knitting needle sizes to modern metric and US, find the number on the needle and match it to a conversion chart. 

Old UK 8 equals 4mm and US 6; old UK 10 equals 3.25mm and US 3. If the needle is unmarked, measure it with a needle gauge instead.

What You Need First

• The needle or vintage pattern showing the old UK number
• A needle gauge, only if the number is worn off or missing
• A few minutes. There's no measuring involved if the number is still legible.

How to Convert Old UK Knitting Needle Sizes: Step by Step

1. Find the number stamped on the needle: Old UK sizes appear as a plain number with no letter usually near the flat end or knob. Higher numbers mean thinner needles the reverse of metric.
2. Match it to the old UK column in a chart: Old UK 10 converts to 3.25mm and US 3; old UK 8 converts to 4mm and US 6 (Vogue Knitting, 2021).
3. Watch for the US gaps. Old UK 11 (3mm), UK 2 (7mm), and UK 1 (7.5mm) have no exact US equivalent. Metric is the only clean match for those three; treat the nearest US number as an estimate, not an exact size.
4. No number visible? Measure it with a needle gauge instead: Slide the needle through the holes until it sits snugly in one, then read that hole's metric size.
5. Treat the metric size as the anchor once you have it. It's the current international standard so converting from metric to US from there is reliable. Converting between two old systems side by side is not.

Quick reference, old UK to metric and US:

The Mistake That Costs You Your Tension

The real trap isn't old UK 13 or 14. Not even close. Those are just the finest sizes on the standard chart, 2.25mm and 2mm.

💡 Pro Tip: Victorian and Edwardian patterns sometimes used needle numbers in the high teens or twenties, sizes below 2mm that no manufacturer makes anymore. 

If a pattern's number falls outside 000 to 14, measure it with a needle gauge instead of guessing.

Bottom Line

A worn or unmarked needle is the only real obstacle here, and a needle gauge solves that in seconds. 

That's the hard part done. Everything else about how to convert old UK knitting needle sizes to metric and US comes down to reading one row of a chart.

Once you've got the metric size from the chart above, plug it into the yarn weight to hook and needle size converter. It returns the matching US, UK/Canada and Japanese sizes for any yarn weight in one lookup. Convert yarn weight to needle and hook size

Other Common Yarn Questions: DK vs Worsted Weight Yarn: Key Differences and When to Swap