Urine Albumin-to-Creatinine Ratio (ACR) Calculator
Calculate the urine albumin-to-creatinine ratio from a spot urine sample and map it to the KDIGO albuminuria categories A1, A2, and A3.
🧪 Lab Value📐 ACR = urine albumin / urine creatinine🏥 Health
Creatinine units
Urine albumin
Urine creatinine
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Urine Albumin-to-Creatinine Ratio (ACR) Calculator | — | ACR = urine albumin / urine creatinine | mg/g or mg/mmol |
Step-by-Step Examples
Example 1
Normal Result
Urine albumin 1.2 mg/dL, urine creatinine 120 mg/dL.
- ACR = (1.2 / 120) × 1000
- ACR = 10 mg/g
- Falls in category A1
✓ ACR 10 mg/g — category A1
Example 2
Moderately Increased
Urine albumin 8 mg/dL, urine creatinine 100 mg/dL.
- ACR = (8 / 100) × 1000
- ACR = 80 mg/g
- Falls in category A2
✓ ACR 80 mg/g — category A2
Example 3
Severely Increased
Urine albumin 55 mg/dL, urine creatinine 90 mg/dL.
- ACR = (55 / 90) × 1000
- ACR = 611 mg/g
- Well above the 300 mg/g threshold
✓ ACR 611 mg/g — category A3
Real-World Applications
Diabetic Kidney Disease Screening
Annual ACR testing is recommended for people with diabetes, since albuminuria often appears before eGFR begins to fall.
CKD Staging
KDIGO staging uses eGFR and albuminuria together in a two-dimensional grid, so ACR is essential to complete the classification.
Cardiovascular Risk
Albuminuria independently predicts cardiovascular events, making ACR informative well beyond kidney disease alone.
Treatment Monitoring
Falling ACR on ACE inhibitors, ARBs, or SGLT2 inhibitors is a recognized marker of treatment response.
Common Mistakes to Avoid
⚠️
Using a single sample to diagnose
Albuminuria varies day to day. KDIGO recommends confirming an abnormal result with two of three samples collected over three to six months.
⚠️
Testing during transient elevations
Exercise, fever, urinary tract infection, heart failure decompensation, marked hyperglycaemia, and menstruation all transiently raise albumin excretion.
⚠️
Substituting a urine dipstick
Standard dipsticks detect total protein and miss the moderately increased range entirely. Only a quantitative albumin measurement gives a usable ACR.
Frequently Asked Questions
What is a normal urine ACR? ▾
Below 30 mg/g — equivalently under about 3 mg/mmol — which corresponds to KDIGO category A1.
Why use a ratio instead of measuring albumin alone? ▾
Urine concentration varies enormously with hydration. Dividing by creatinine, which is excreted at a relatively steady rate, corrects for that dilution.
What replaced the terms microalbuminuria and macroalbuminuria? ▾
KDIGO now uses categories A1, A2, and A3, since the older terms implied a sharp biological boundary that does not exist — albuminuria risk is continuous.
When should the sample be collected? ▾
A first morning void is preferred because it minimises the effect of upright posture and daytime activity on albumin excretion.
Does a high ACR always mean kidney disease? ▾
No. Transient causes are common, which is why confirmation over months matters. Persistent elevation, however, is a meaningful marker of kidney damage.