Albumin-to-Creatinine Ratio (ACR) Calculator
Enter your urine albumin and creatinine concentrations to get your albumin-to-creatinine ratio (ACR) instantly. The result is classified against the KDIGO 2024 albuminuria categories (A1, A2, A3) so you can see where your kidney health stands. Switch units freely: albumin can be entered in mg/dL, mg/L, or g/L; creatinine in mg/dL, mmol/L, or umol/L. ACR is the standard first-morning-urine test recommended for CKD screening in people with diabetes, hypertension, or a family history of kidney disease.
What is the albumin-to-creatinine ratio (ACR)?
The albumin-to-creatinine ratio (ACR) measures how much albumin - a protein made by the liver - is being spilled into the urine relative to the amount of creatinine, a muscle waste product. Healthy kidneys filter almost all albumin back into the blood, so a high ACR means the kidney filter is damaged or leaking. Because creatinine production is relatively constant throughout the day, dividing albumin by creatinine corrects for urine dilution and turns a single spot urine sample into a reliable estimate of 24-hour albumin excretion. An ACR below 30 mg/g is considered normal; 30-299 mg/g is moderately increased (formerly called microalbuminuria); and 300 mg/g or above is severely increased (formerly macroalbuminuria).
How to collect a urine sample for ACR testing
The preferred sample is the first-morning void, collected after cleansing the genital area. This sample avoids exercise-induced or orthostatic albuminuria that can temporarily raise ACR in the afternoon. Random or spot samples taken at any time of day are acceptable and are used routinely in clinical practice, but they have slightly more day-to-day variability. Pour a small amount of urine into a sterile container and refrigerate it until the test. Because of normal biological variation, a single elevated ACR result should be confirmed with at least two additional tests over the next three months before a clinical diagnosis of persistent albuminuria is made.
ACR and chronic kidney disease (CKD)
The 2024 KDIGO guideline classifies CKD using both glomerular filtration rate (GFR) categories (G1-G5) and albuminuria categories (A1-A3). These two dimensions together give a more complete picture of kidney health and prognosis than either measure alone. Even a normal eGFR alongside persistent A2 or A3 albuminuria warrants monitoring and risk-factor management, because albuminuria is an independent predictor of CKD progression, cardiovascular events, and all-cause mortality. People with diabetes or hypertension should have ACR measured at least once a year. If two consecutive results are elevated, treatment to reduce albuminuria - including blood pressure control, SGLT2 inhibitors, or renin-angiotensin system blockade - can slow kidney decline.
Factors that affect ACR results
Several non-kidney factors can temporarily raise or lower ACR. Vigorous exercise, fever, urinary tract infection, heart failure, and extreme dehydration can all increase albumin excretion transiently. High fluid intake can dilute the sample and lower ACR. Menstruation can contaminate the sample with blood protein. Because women naturally have lower muscle mass and produce less creatinine per day, their creatinine concentration in a spot sample tends to be lower, which can push the calculated ratio up relative to men. This is why some guidelines have historically used sex-specific reference intervals, although KDIGO 2024 uses a single 30 mg/g threshold. If your result is borderline, your clinician can ask for a timed overnight urine collection to remove the dilution variable.
KDIGO 2024 Albuminuria Categories
| Category | ACR (mg/g) | ACR (mg/mmol) | Description | Clinical action |
|---|---|---|---|---|
| A1 | < 30 | < 3.4 | Normal to mildly increased | Routine screening if at risk |
| A2 | 30 - 299 | 3.4 - 34 | Moderately increased | Confirm on repeat; manage risk factors |
| A3 | >= 300 | >= 34 | Severely increased | Nephrology referral; treat underlying cause |
Based on the 2024 KDIGO Clinical Practice Guideline for Evaluation and Management of Chronic Kidney Disease. ACR from a spot urine (preferably first morning void).
Frequently asked questions
What is a normal ACR level?
According to KDIGO 2024 guidelines, an ACR below 30 mg/g (or about 3.4 mg/mmol) is classified as A1 and considered normal to mildly increased. This is the expected result in people without kidney disease. Values between 30 and 299 mg/g are A2 (moderately increased), and 300 mg/g or above is A3 (severely increased).
Can a high ACR be temporary?
Yes. Vigorous exercise in the preceding 24 hours, fever, a urinary tract infection, dehydration, and heart failure can all temporarily raise urine albumin excretion without indicating chronic kidney damage. This is why guidelines recommend confirming an elevated ACR on at least two separate tests over three months before making a diagnosis of persistent albuminuria.
What is the difference between ACR and total protein-to-creatinine ratio (PCR)?
ACR measures only albumin, which is the predominant protein lost in early diabetic and hypertensive kidney disease. PCR measures all urine protein including albumin, globulins, and Bence-Jones proteins. ACR is more sensitive for early CKD screening in people with diabetes or hypertension; PCR is often preferred when investigating conditions that cause non-albumin proteinuria, such as myeloma or tubular disorders.
Why is creatinine included in the ratio?
Urine albumin concentration varies throughout the day as fluid intake changes. A dilute urine after drinking a lot of water will have a lower albumin concentration even if the kidney is leaking the same amount. Dividing by creatinine - which is excreted at a fairly constant rate - corrects for this dilution effect and makes a single spot urine sample equivalent to a 24-hour collection for most clinical purposes.
Who should be screened for albuminuria?
KDIGO 2024 recommends annual ACR screening for adults with diabetes, hypertension, obesity, cardiovascular disease, a family history of CKD, or a history of acute kidney injury. People with lupus or other conditions that can affect the kidneys, and those who are 65 or older, may also benefit from periodic screening. A single normal result does not rule out future disease, so repeat testing according to your clinician's guidance is important.