How long does it take to pass a kidney stone: The length of time it takes to pass a kidney stone varies depending on the size and location of the stone. In most cases, a stone smaller than 4mm will pass within a few days to a week. Larger stones may take several weeks to a few months to pass. It's important to drink plenty of water to help flush the stone out of the body. If you experience severe pain or have difficulty passing the stone, seek medical attention.