I found an old pair of knitting needles that I might use for a project now but, I don’t know its size. Is there any way i can find its sizing soon?
Go to your local yarn store/joanns/michaels/hobby lobby/hancocks/walmart - any place that sells needles, and look for a needle gauge, will usually be combined with a handy ruler. Or poke a hole in paper very carefully and measure the diameter across the hole with a mm ruler/measure.