The diameter is four inches. Jill, I think I was in such a rush to light it that I forgot to trim the wick to 1/4 inch! I just lit it again about 20 minutes ago (after trimming) and the flame seems to be better. After this burn I will take your and Beth's advice and let it cure for another 3 days and retest. But still, even now, the CT and HT are still very faint. I guess time will tell if the throw gets better. But back to the wick question, for a jar this size, would it make more sense to single or double wick? Thanks for the advice!