US and Metric Needle Systems

This knitting needle converter translates between the US numbering system and exact metric diameters in millimeters. The conversion table follows the Craft Yarn Council standard, which pairs each US size with a precise mm measurement — for example US 5 equals 3.75 mm and US 8 equals 5.0 mm.

Non-Standard Sizes

If you enter a size that is not on the standard table, the converter finds the nearest standard size and reports the difference in millimeters. Sizes usually run in half-steps, so a quarter-millimeter gap is common and harmless.

Choosing the Right Needle

Patterns specify a size to achieve the right gauge, but your personal tension matters more. If your gauge swatch is off, moving up or down a half size is the standard fix — and now you know exactly what that means in millimeters.