A kidney stone can range from less than 1/5 of an inch to nearly the size of a golf ball. Very small stones can be minuscule and resemble sand grains, states the National Institute of Diabetes and Digestive and Kidney Diseases. When kidney stones are very large, they can be difficult to pass and can cause severe pain and blood in the urine.
A kidney stone develops due to urine containing too many crystal-forming substances, including calcium and uric acid. The size of the kidney stones can determine if it passes without problems. There is a 90 percent chance that a stone that is less than 1/5 of an inch will pass without any difficulty. If the stone varies from 1/5 to 2/5 of an inch, the chance that it may pass on its own decreases to 50 percent, as stated by WebMD. Kidney stones larger than these sizes may require different treatment options, such as shock wave lithotripsy or percutaneous nephrolithotomy (surgical removal of stones).