How Long Does It Take to Pass a Kidney Stone?

Quick Answer

The time it takes to pass a kidney stone depends primarily on its size and location. Stones smaller than 4 mm have about an 80% chance of passing on their own within 1–2 weeks. Stones between 4–6 mm may take 2–4 weeks and pass about 60% of the time without intervention. Stones larger than 6 mm usually require medical procedures and rarely pass naturally.

Passage Time by Stone Size

Stone Size	Chance of Passing Naturally	Typical Timeline
< 2 mm	~95%	Days to 1 week
2–4 mm	~80%	1–2 weeks
4–6 mm	~60%	2–4 weeks
6–7 mm	~20%	4–6 weeks (often needs treatment)
> 7 mm	~5%	Rarely passes; treatment required

What Happens as a Stone Passes

A kidney stone's journey from the kidney through the ureter to the bladder is the painful part. Once a stone reaches the bladder, it usually passes through the urethra within a few days with minimal discomfort. The intense, wave-like pain known as renal colic occurs when the stone moves through the narrow ureter, which is only 3–4 mm wide.

Pain typically comes in waves lasting 20–60 minutes as the ureter spasms around the stone. Many people describe kidney stone pain as among the most intense they have ever experienced.

Factors That Affect Passage Time

Stone size. This is the most important factor. Every additional millimeter significantly reduces the odds of spontaneous passage and increases the time required.

Stone location. Stones already in the lower ureter (near the bladder) pass faster than those still in the upper ureter or kidney. A stone in the distal ureter may pass within days.

Hydration. Drinking 2–3 liters of water per day increases urine output and helps push the stone through the urinary tract. This is the most commonly recommended home measure.

Medication (medical expulsive therapy). Alpha-blockers like tamsulosin relax the smooth muscle of the ureter, which can speed passage and reduce pain, particularly for stones 5–10 mm.

Medical Treatment Options

• Extracorporeal shock wave lithotripsy (ESWL): Uses sound waves to break stones into smaller fragments. Recovery takes 1–2 weeks. Best for stones under 2 cm in the kidney or upper ureter.
• Ureteroscopy: A thin scope is inserted through the urethra to locate and remove or laser-fragment the stone. Recovery takes 1–2 weeks.
• Percutaneous nephrolithotomy: A surgical procedure for large stones (> 2 cm). Recovery takes 1–2 weeks in hospital, 2–4 weeks total.

Prevention Tips

• Drink enough water to produce at least 2.5 liters of urine per day.
• Reduce sodium intake to under 2,300 mg daily, as excess sodium increases calcium in the urine.
• Eat adequate dietary calcium (from food, not supplements), which paradoxically reduces stone risk by binding oxalate in the gut.
• Limit animal protein, which raises uric acid and reduces urinary citrate.