UACR calculator: urine albumin-to-creatinine ratio in mg/g and mg/mmol

The urine albumin-to-creatinine ratio, UACR or ACR, is the urine test for early kidney damage. Some reports print the ratio. Others print only the two numbers it comes from, a urine albumin and a urine creatinine, and leave the division to you. Enter both from the same sample below to get the ratio in mg/g and mg/mmol, and the KDIGO albuminuria category it falls in.

The formula

UACR (mg/g) = urine albumin (mg/L) ÷ urine creatinine (g/L)

UACR (mg/mmol) = urine albumin (mg/L) ÷ urine creatinine (mmol/L)

Labs usually print urine creatinine in mg/dL, so divide it by 100 to get g/L first. An albumin of 18 mg/L with a creatinine of 120 mg/dL (1.2 g/L) gives 15 mg/g. Urine albumin in µg/mL is the same number as mg/L, and mg/dL is ten times smaller.

The two units of the ratio differ by a fixed factor. The KDIGO 2024 chronic kidney disease guideline gives it:

mg/mmol = mg/g × 0.113

The calculator works the mg/mmol figure out from creatinine’s molar mass, 113.12 g/mol, which gives the same 0.113.

Why the ratio and not the albumin alone

How concentrated a urine sample is depends on how much you drank. The same albumin loss reads high in a concentrated morning sample and low in a dilute one after a lot of water. KDIGO notes that spot samples can over- or underestimate urine albumin for this reason, and that dividing by creatinine reduces the error. Creatinine passes into the urine at a fairly steady rate, so it rises and falls with concentration the same way albumin does, and the dilution cancels out.

Here is the same person on two days:

The albumin concentration halved. The ratio didn’t move. That is why KDIGO asks labs to report the ratio, and why it is the number to track.

The categories

KDIGO grades albuminuria in three categories:

KDIGO calls the mg/mmol cutoffs approximate equivalents. They are rounded: 30 mg/g is 3.4 mg/mmol, not 3. A result between 3.0 and 3.4 mg/mmol is A2 on one scale and A1 on the other. The calculator reads the scale that matches the creatinine unit you entered, since a lab reporting creatinine in mmol/L usually reports the ratio in mg/mmol, and it tells you when the two scales disagree.

Watch the units in your history. A result of 30 is the top of A2 in mg/mmol and the bottom of it in mg/g, and 300 mg/g is 34 mg/mmol.

Worked examples

The second and third rows have the same albumin concentration and land in different categories. The urine in the second was about four times as concentrated.

If your report gives albumin as below a limit, such as “<3 mg/L”, there’s no exact ratio to calculate. Entering the limit gives the highest the ratio could be.

One result is not a diagnosis

UACR is one of the noisiest tests on a lab report. The ADA Standards of Care put the biological variation in urine albumin at more than 20% between measurements. For that reason the ADA says two of three samples collected within 3 to 6 months should be abnormal before anyone is considered to have moderately or severely increased albuminuria. The categories describe albuminuria that persists.

How the sample was collected matters too. KDIGO prefers a first morning void, the first urine after you get up, because it varies less from day to day. A random sample taken at a clinic visit is acceptable, and KDIGO suggests confirming a random result of 30 mg/g or more with a later first morning sample.

Several things raise UACR for a while without any change in your kidneys. The ADA lists exercise in the past 24 hours, infection, fever, heart failure, very high blood sugar, menstruation, and very high blood pressure. KDIGO adds blood in the urine and a urinary tract infection. If any of these applied, note it next to the result and expect a repeat.

The creatinine half moves too. KDIGO notes that women and people with low body weight excrete less creatinine, which gives a higher ratio for the same albumin loss. High protein intake or exercise raises urine creatinine and pulls the ratio down; a low-protein diet pushes it up.

When the calculator differs from your report

• Rounding. Labs often print mg/g as a whole number and may round the inputs before dividing.
• A different factor. Some reports convert with 0.113 and some with 8.84 the other way. The results agree to within rounding.
• Two different tests. “Microalbumin” on a report can mean the ratio in mg/g or the albumin concentration alone in mg/L. Only the ratio has the categories above.

Tracking it over time

A single UACR says little. A history of results collected the same way, read next to your eGFR, says a lot. How to track your urine albumin (UACR) over time covers what counts as a real change, the medications that lower it, and how to chart it. The eGFR calculator covers the other half of kidney staging, and the lab unit converter converts urine creatinine between units.

UACR in HealthViewer

HealthViewer is a lab results tracker that runs on your own computer. It imports urine albumin results from lab report PDFs, MyChart downloads, and direct connections to your health system, and charts each test over time in Trends. The ratio and the albumin concentration alone are kept as separate tests.

If your lab reports urine albumin and urine creatinine but not the ratio, you can calculate it in Settings → Derived Tests. Create a formula A / B, with A as Microalbumin (Urine) in mg/L and B as Creatinine (Urine) in g/L, and a date window of 0 so both come from the same day. Creatinine in mg/dL is converted first, and the result is the ratio in mg/g.

Everything stays in an encrypted file on your computer, with no account and no cloud service. Getting Started walks through the first import.

This calculator is for understanding your lab report, not for diagnosis or treatment. Ask your clinician what your UACR means for you.