What size kidney stone will pass on its own?

As anyone who’s passed a kidney stone knows, it can be a very painful experience, depending on the size. If the stone is small – less than 5 mm – and not causing any pain, there is a good chance that it will pass on its own after it falls into the ureter. Such stones may be followed with watchful waiting. This means that the stone is not actively treated, but instead your doctor keeps a check on the stone to be sure that it is not growing or changing. This can be done with periodic X-rays.