I am wondering if anyone could advise me, I have a pattern for booties (cast on 30sts) to be done on 4.25 needles, as I haven't got this size and neither has my local shop I was wondering if I could use 4mm or 4.5mm and do I need to adjust the pattern. Thank you xx
Sure, do a gauge swatch and see which one comes closer to the gauge you need. The size isn't different enough to have to adjust the pattern.
What is the name of the pattern? Have a link?
The pattern should give a gauge of so many sts. per 4"/10cm. or similar. You might find that different size needles are exactly right for whatever the gauge is.