Most small kidney stones pass on their own within a few weeks, especially with pain relief and medical expulsive therapy (tamsulosin) for distal stones of 5–10 mm. Larger stones and those high in the ureter are more likely to need a procedure.
How to use the Kidney Stone Passage Calculator
- Stone size (largest diameter)
- Location
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the stone’s largest diameter and where it is. Seek urgent care for fever, uncontrolled pain or a single kidney.
Inputs explained
| Field | What to enter |
|---|---|
| Stone size (largest diameter) | In mm |
| Location | Choose one: Proximal ureter, Mid ureter, Distal ureter / UVJ |
Example values
How the main result changes when Stone size changes and everything else stays at the example values above:
| Stone size (largest diameter) (mm) | Chance of passing spontaneously (%) |
|---|---|
| 2.5 | 87 |
| 3.75 | 81 |
| 5 | 65 |
| 6.25 | 63 |
| 7.5 | 55 |
| 10 | 30 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Approximate spontaneous passage by size: ≤ 4 mm about 80%, 5–7 mm about 60%, 7–9 mm about 48%, > 9 mm about 25%
Distal ureteral stones pass more often than proximal ones
Worked example
Inputs — Stone size (largest diameter): 5 mm; Location: Distal ureter / UVJ.
Results — Chance of passing spontaneously = 65 %; Typical time to pass = About 3 weeks.
Key terms
- UVJ
- Ureterovesical junction, where the ureter enters the bladder.
- MET
- Medical expulsive therapy.
Frequently asked questions
What size kidney stone can pass naturally?
Most stones under 5 mm pass; about half of 5–10 mm stones do.
How long should I wait?
Usually up to 4–6 weeks if pain is controlled and there is no infection.
What helps a stone pass?
Pain relief, staying hydrated and, for distal stones, tamsulosin if your doctor recommends it.