Urinary Calcium (Spot Ca/Cr + 24-hour Excretion)
Urinary-calcium assessment: the calciuria step in the nephrolithiasis / hypercalciuria workup, either a spot Ca/Cr ratio against age-band thresholds or a 24-hour excretion against sex/weight thresholds.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Mode
- Spot Ca/Cr ratio
- Urine calcium
- 30
- Urine creatinine
- 100
- Age band
- Adult / older child (> 0.20 mg/mg)
Result: Spot Ca/Cr 0.3 mg/mg (≈ 0.85 mmol/mmol) — above the adult (> 0.20) threshold (hypercalciuria).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Spot
- Ca/Cr (mg/mg, molar ≈ ×2.82): hypercalciuria above the adult > 0.20 or the Sargent pediatric upper limits (< 7 mo 0.86, 7–18 mo 0.60, 19 mo–6 y 0.42 mg/mg).
- 24-hour
- 24-hour urine calcium > 250 mg/day (women), > 300 mg/day (men), or > 4 mg/kg/day is hypercalciuria. The calciuria step in the nephrolithiasis workup; decision support, not an order.
What you enter
- Mode (spot ratio or 24-hour excretion)
- Urine calcium (spot; same mass unit as creatinine)
- Urine creatinine (spot; same mass unit as calcium)
- Age band (spot)
- 24-hour urine calcium
- Body weight (24-hour)
- Sex (24-hour)
How this is calculated
Pearle MS, Goldfarb DS, Assimos DG, et al. Medical management of kidney stones: AUA guideline. J Urol. 2014;192(2):316-324. Pediatric bands: Sargent JD, Stukel TA, Kresel J, Klein RZ. Normal values for random urinary calcium to creatinine ratios in infancy. J Pediatr. 1993;123(3):393-397. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.