Confused about yarn weight and needle sizes for knitting/crocheting

I am a little confused about yarn weight and needle/hook sizes. I found a chart online that shows standards and guidelines for these, but right now I am working on a pattern (for a cupcake) that has me working with dk yarn and size US1 & US2 needles, and according to that chart that would be way off (chart says i should be using fingerling yarns with those size needles). How important is it to follow those standards/guidlines?? Is the chart mainly for finished guage sizes or is there another reason to follow it?? Just wondering because I just bought some dk weight yarn and just realized the pattern I am going to be using for booties called for worsted weight, and according to the chart I shouldnt be using a size E crochet hook with that yarn… so confused.

It mostly depends on the finished fabric you’re going for. A cupcake, I imagine, would require a dense fabric to give it shape so you’d use a smaller needle for a tighter stitch.

Lace often uses a very large needle compared to the thickness of the yarn to give a loose, drapey fabric.

The pattern gauge is what you want to aim for in order for the finished product to turn out to be the proper size.

gauge is what matters.

as Ingrid has pointed out, sometimes a much smaller than expected needle size is called for–but what matters is the gauge.

some designers KNIT tightly (and they might use a size 8 (US) needle to get the same gauge i can get on a size 6–

or the opposite… they might require a size 3 to get the same gauge as i do on a size 6!
(i have friends who use size 0 needles for socks… but my socks, knit on size 2’s have a tighter gauge/fabric!)

Needle size is always just a recommendation/suggestion.

you can use any size needles–so long as you end up with the right gauge (and the right kind of fabric!)