Needle size substitution on socks?

Hi, I am relatively new to knitting. If a sock pattern asks for a 2.5 mm double pointed needles, can I use 2.25 mm?
Or 2. 75mm? Or does such a small change mean the size would be way different?

In general terms using a different size will affect the size of your socks.

HOWEVER, everyone’s gauge is different. If you are a tight knitter you may need to go up a needle size or if you are a loose knitter then you may need to go down. You can swatch to see what works best for you, but keep in mind that socks are knit in the round and knitting a flat gauge won’t be a perfect measure.

Here’s a method to test your gauge for in the round while knitting flat.

Thanks SO much, Jan. This is great information to know on my knitting journey!

Glad I could help!

As an example to what I said about gauge…I’m a loose knitter and I’d use a US 0 (2mm) to knit socks.

So I guess I would go with a 2.75 for this pattern as I knit on the tight side I think.

You can give it a try. If you don’t like the fabric or it’s too loose or too tight you can rip and start again. It’s a pain in the neck, but is really the best way to learn what works for you. I made my first pair with a 2 and they were too loose and didn’t last long. Gradually realized I needed a 0.