How can you tell from a pattern what diameter circular needles you should use? I'm wanting to knit a toddler sweater where the finished chest measurement would be 26.5". So what diameter of circs should I use, and how can I know for future reference?
You don't want one larger than the diameter you'll be knitting (though there are exceptions), so you can use a 24" for this and larger projects as well, such as a sweater for yourself.
24 inch circular length since your finished measurement is 26.5. If you are knitting in the round you need to have the length shorter than your finished product circumference. Hope this helps.