Is 2-3mm considered to be a big kidney stone and can it pass without you knowing it?

Kidney stones: The size of the stone does not correlate with the degree of suffering very well. The extreme pain is caused by spasm of the ureter as the stone passes through. Some stones pass without causing ureteral colic pain. The likelihood of passing the stone all the way to the bladder quickly is increased with 2-3 mm stones though.

Not big: A 2-3 mm kidney stone is not considered large but still can cause a tremendous amount of pain. These smaller stones will usually pass. It is stones over 3mm that may need help passing although even some larger stones will pass on their own as well.