Enter the urine calcium concentration and the urine creatinine concentration (from the same spot urine sample) into the calculator. The calculator will evaluate the urine Ca/Cr ratio (calcium-to-creatinine ratio).

Urine Ca/Cr Ratio Calculator

Note: Use urine (not blood/serum) results from the same sample.

This tool converts your entries to consistent units before calculating. If you change a unit dropdown after typing a value, update the number to match the unit shown on your lab report.

Enter any 2 values to calculate the missing variable

Unit tip: Most urine creatinine results are reported in mg/dL or mmol/L. µmol/L is uncommon for urine—double-check your report to avoid accidentally entering serum creatinine.

Common reporting formats include mg/mg (mass ratio) and mmol/mmol (molar ratio). Select the unit you want for the ratio field.

Medical disclaimer: Educational use only. Not medical advice or a diagnosis. Do not start, stop, or change medications or supplements (including calcium/vitamin D) based on this tool. Use your lab’s reference range; interpretation varies by age (especially children), pregnancy status, hydration, diet, and lab methods. Discuss abnormal results with a licensed clinician.

Ca/Cr Ratio Formula

\text{Ca/Cr}=\frac{\text{Ca}}{\text{Cr}}

Variables:

  • Ca/Cr is the urine calcium-to-creatinine ratio (commonly reported as mg/mg or mmol/mmol, depending on how your lab reports calcium and creatinine)
  • Ca is the urine calcium concentration (commonly mg/dL or mmol/L)
  • Cr is the urine creatinine concentration (commonly mg/dL or mmol/L; some reports may use µmol/L)

To calculate the urine Ca/Cr ratio, divide the urine calcium concentration by the urine creatinine concentration (from the same urine sample). Make sure both values are in consistent units (this calculator converts units automatically before calculating).

How to Calculate Ca/Cr Ratio?

The following steps outline how to calculate the urine Ca/Cr ratio.

  1. First, determine the urine calcium concentration (e.g., mg/dL) from a spot urine sample.
  2. Next, determine the urine creatinine concentration (e.g., mg/dL) from the same spot urine sample.
  3. Next, use the formula from above: Ca/Cr = Ca ÷ Cr.
  4. Finally, calculate the Ca/Cr ratio.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

urine calcium (mg/dL) = 5

urine creatinine (mg/dL) = 6

Ca/Cr = 5 ÷ 6 = 0.8333 mg/mg

Frequently Asked Questions (FAQ)

What is the significance of the Ca/Cr Ratio?

The urine calcium-to-creatinine (Ca/Cr) ratio is a spot urine measurement used to estimate urinary calcium excretion while accounting for urine concentration. It is commonly used as a screening tool for hypercalciuria (high urinary calcium), especially in evaluations related to kidney stones or disorders of calcium metabolism. Interpretation is age-dependent (especially in children), and your lab’s reference range matters.

Can the Ca/Cr Ratio indicate specific health issues?

Yes. An elevated urine Ca/Cr ratio can suggest hypercalciuria, which may be seen with conditions such as hyperparathyroidism, vitamin D excess, certain granulomatous diseases, or idiopathic hypercalciuria. Interpretation depends on age, diet, hydration status, and laboratory reference ranges, and abnormal results often require follow-up testing (sometimes including a 24-hour urine collection).

How often should the Ca/Cr Ratio be tested?

The frequency of testing depends on the clinical situation. It may be ordered by a healthcare provider to evaluate suspected hypercalciuria, monitor treatment, or assess kidney-stone risk.

Are there any preparations required before testing for the Ca/Cr Ratio?

Sometimes. Diet (including calcium intake) and supplements/medications can affect urinary calcium. Some protocols prefer a first-morning urine sample. Follow the specific instructions provided by your healthcare provider or laboratory.

Further reading (suggested)

  • Check your lab report’s reference range notes for urine calcium, urine creatinine, and the Ca/Cr ratio.
  • For general patient-friendly explanations, look up “urine calcium test” and “urine creatinine test” on reputable health resources (e.g., MedlinePlus or major hospital laboratory guides).
  • For unit conversion background, consult standard clinical chemistry references (molecular weights and SI–conventional unit conversions).