Albumin Creatinine Ratio Calculator

Check the specimen before the numbers

A urine albumin-to-creatinine ratio compares two concentrations measured in one urine specimen. A spot sample is sufficient for routine assessment; a first-morning sample is preferred, but a random sample can also be used. The ratio reduces the effect of urine dilution compared with albumin concentration alone. NIDDK’s urine albumin guidance explains the specimen and calculation.

“Microalbumin”, “microalb/creat” and “calc microalb creat rnd” may appear as laboratory shorthand. Microalbumin refers to measuring small amounts of albumin, rather than a different protein. Use the urine albumin value, not total urine protein. A blood or serum albumin result cannot replace it, and serum creatinine cannot replace urine creatinine in this calculation. See MedlinePlus on the microalbumin creatinine ratio.

If your report already includes a UACR, compare its units and reference interval first. Recalculating from rounded component values can produce a slightly different answer.

The formula changes with the input units

The albumin creatinine ratio formula is albumin concentration divided by creatinine concentration after matching the volume units and converting creatinine mass to grams:

For the common combination of albumin in mg/L and creatinine in mg/dL:

Suppose urine albumin is 30 mg/L and urine creatinine is 100 mg/dL. Creatinine is 1 g/L, so 30 mg/L divided by 1 g/L is 30 mg/g. Both measurements refer to the same urine volume; the volume cancels.

If albumin is instead 30 mg/dL, that is ten times as much albumin as 30 mg/L. With the same creatinine value, the ratio becomes 300 mg/g. Leaving out this unit conversion creates a tenfold error.

Albumin in µg/mL has the same numerical value as mg/L. For creatinine in mmol/L, dividing albumin in mg/L directly by creatinine in mmol/L gives mg/mmol. The calculator also accepts urine creatinine in g/L and µmol/L.

The two result units are related by:

The factor uses creatinine’s molecular weight of 113.12 g/mol, reported by PubChem. Thus the default 30 mg/g result is 3.3936 mg/mmol, displayed as 3.39 mg/mmol. Small nonzero or very large results use scientific notation so that rounding does not turn a small value into zero.

Read the category alongside the laboratory report

This calculator follows the mg/g ranges in KDIGO 2024, Table 3:

The category compares the entered decimal measurements before result rounding. For example, exactly 300 mg/g is A2 under this table’s convention, while a value just above 300 is A3. Some other summaries use A3 starting at 300 mg/g; compare results with the convention used by your laboratory.

KDIGO also lists approximate SI ranges of below 3, 3–30 and above 30 mg/mmol. Those convenient cutoffs are not exact mass-to-molar conversions. To avoid changing a category when you change input units, this calculator always assigns the category on the labelled mg/g basis. Near a boundary, your laboratory’s mg/mmol category may therefore differ. The scale shows those mg/g boundaries and uses a logarithmic axis; it is a category guide rather than a kidney-risk score.

The KDIGO guideline provides the ranges in Table 3 (page S137) and explains confirmation in Practice Point 1.3.1.2. A result at or above 30 mg/g needs clinical review and may need confirmation with a first-morning urine sample. A single ratio does not establish chronic kidney disease. Assessment also depends on persistence, eGFR and the clinical context.

When the ratio is too low to calculate

“Unable to calculate” can mean that albumin or creatinine lies outside an assay’s measuring range. It does not necessarily mean the ratio is zero or that the kidneys are healthy. Corewell Health’s laboratory reporting explanation describes why an out-of-range component may prevent reporting a ratio.

If a report says albumin <3 mg/L, entering 3 would treat an upper limit as an exact measurement. Entering zero would also invent a value. This calculator accepts exact numbers only; ask the laboratory or clinician to interpret a censored result.

For illustration, if creatinine is exactly 100 mg/dL and albumin is <3 mg/L, the available information implies ACR <3 mg/g, not an exact ratio of 3 or 0. If creatinine is also reported with an inequality, the same simple bound may not apply. Follow the laboratory’s interpretation rather than replacing missing measurements.

Why a repeat test can differ

Exercise, urinary infection, menstruation and blood in urine can affect albumin results. Differences in creatinine excretion can also affect the ratio. These influences are listed in KDIGO Table 16. Tell your clinician about the circumstances of collection and follow their instructions for any repeat sample. Do not change treatment based on this calculator.

The entered measurements are processed in your browser. Copy creates a summary containing both input units and results; Print / PDF uses the page’s export control. Reset restores the illustrative values of 30 mg/L albumin and 100 mg/dL creatinine, which are examples rather than personal recommendations.