Knitting needle size guide
4 mm knitting needle (6)
4 mm is the metric diameter. The Craft Yarn Council pairs it with 6. Use the millimeter marking when labels disagree.
Immediate answer
4 mm → 6
- Diameter
- 4 mm
- CYC US label
- 6
Relative diameter visualization—not a physical on-screen ruler.
CYC starting range
Often paired with category 3 (light)
- Check the pattern gauge first.
- Make and measure a gauge swatch.
- Change tool size if the swatch misses gauge.
How to use this size
Treat the label as a starting point.
- 1. Read the pattern. Note the stated tool, yarn, stitch pattern, and target gauge.
- 2. Match millimeters. If a letter or number conflicts, use 4 mm.
- 3. Swatch and wash. Measure the fabric the same way the finished project will be treated.
- 4. Adjust one step. Use a smaller tool for more stitches per inch or a larger one for fewer.
Source notes
Last reviewed September 1, 2026
- Craft Yarn Council: Hooks & Needles Metric and US hook and needle size tables; gauge-swatch qualification.
- Craft Yarn Council: Standard Yarn Weight System Yarn weight categories, common names, gauge ranges, and tool ranges.