Calculate the urine oxalate/creatinine ratio from oxalate and creatinine concentrations in mg/L or mmol/L, shown as mg/g or mmol/mol.

Oxalate/Creatinine Ratio Calculator

Enter oxalate and creatinine to calculate the ratio (choose the same reporting unit your lab uses).

mg/g

Medical note: This calculator is for education only and is not a diagnosis. Labs report oxalate/creatinine ratios in different units and reference ranges (often varying by age and lab method). Discuss results with a clinician—seek urgent care for severe flank pain, fever, vomiting, or blood in urine.

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Oxalate/Creatinine Ratio Formula

Oxalate/creatinine ratios are commonly reported as mg/g creatinine or mmol/mol creatinine. Use the formula that matches the reporting unit.

\begin{aligned}
R_{mg/g} &= \frac{O_{mg/L}}{C_{g/L}} \\
R_{mmol/mol} &= \frac{O_{mmol/L}}{C_{mmol/L}} \times 1000
\end{aligned}

Variables:

  • R is the oxalate/creatinine ratio (commonly reported as mg/g or mmol/mol)
  • O is the oxalate concentration in urine (mg/L or mmol/L)
  • C is the creatinine concentration in urine (g/L for mg/g reporting, or mmol/L for mmol/mol reporting)

To calculate the ratio, your oxalate and creatinine values must be in the correct units for the reporting format (for example, mg/g uses creatinine in grams, while mmol/mol uses a molar ratio). Reference ranges and interpretation depend on whether testing is from a spot urine sample or a 24-hour urine collection, and on the lab’s methods.

What is the Oxalate/Creatinine Ratio?

The oxalate/creatinine ratio is a clinical measurement that may help clinicians evaluate suspected hyperoxaluria and kidney stone risk in context. Oxalate is a natural substance found in many foods, and higher urinary levels can contribute to certain types of kidney stones. Creatinine is a waste product produced by muscles; its urinary excretion is often relatively steadier than many analytes but can still vary with muscle mass, kidney function, hydration, and collection conditions. Clinicians may use a spot urine ratio in some situations, while a 24-hour urine test may be preferred for broader stone-risk assessment.

How to Calculate Oxalate/Creatinine Ratio?

The following steps outline how to calculate the Oxalate/Creatinine Ratio.

  1. First, measure the oxalate concentration in urine (O).
  2. Next, measure the creatinine concentration in urine (C).
  3. Choose the ratio reporting unit (commonly mg/g or mmol/mol) and convert units if needed.
  4. Calculate the oxalate/creatinine ratio using the matching formula.
  5. After inserting the values 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.

Oxalate concentration in urine (O) = 45 mg/L

Creatinine concentration in urine (C) = 150 mg/L

Oxalate/Creatinine Ratio (mg/g) = 45 mg/L ÷ 0.150 g/L = 300 mg/g