Calculate spot urine protein-to-creatinine ratio (PCR) and albumin-to-creatinine ratio (ACR). Classifies proteinuria severity and estimates 24-hour protein excretion.
The urine protein-to-creatinine ratio (PCR) is a convenient spot urine test that estimates 24-hour protein excretion without the burden of a timed collection. It has become the standard screening tool for proteinuria — one of the earliest and most important markers of kidney disease. A normal PCR is below 0.15 g/g (150 mg/g), while nephrotic-range proteinuria is defined as ≥3.5 g/g, indicating severe glomerular damage.
This calculator accepts spot urine protein and creatinine values, computes the PCR in both g/g and mg/g, classifies severity into five categories (normal to nephrotic), and estimates equivalent 24-hour protein excretion. The correlation between spot PCR and 24-hour collection is approximately r = 0.93, making it a reliable surrogate in most clinical settings. The calculator also computes the albumin-to-creatinine ratio (ACR) when urine albumin is provided — a more sensitive marker for early diabetic nephropathy.
Proteinuria is not Just a lab value — it is an independent predictor of cardiovascular mortality, CKD progression, and all-cause mortality, even at mild levels. Every doubling of proteinuria is associated with a 29% increase in cardiovascular mortality (PREVEND study). Early detection through PCR screening enables timely intervention with ACE inhibitors/ARBs, blood pressure control, and SGLT2 inhibitors, which can dramatically slow kidney disease progression.
Spot urine PCR has replaced 24-hour collections as the primary proteinuria screening method because of convenience and comparable accuracy. This calculator classifies results, estimates 24-hour equivalents, computes ACR for diabetic screening, and provides clinical action recommendations — making it a practical reference for both patients and clinicians. Keep these notes focused on your operational context. Tie the context to the calculator’s intended domain.
PCR (g/g) = Urine Protein (mg/dL) ÷ Urine Creatinine (mg/dL). Estimated 24h protein (g) = PCR × Average daily creatinine (Male: 1.5g, Female: 1.2g). ACR (mg/g) = Urine Albumin (mg/dL) ÷ Urine Creatinine (mg/dL) × 1000. Normal PCR < 0.15 g/g. Nephrotic range ≥ 3.5 g/g.
Result: PCR 0.45 g/g — Mildly elevated proteinuria
PCR = 45/100 = 0.45 g/g (450 mg/g), classifying as mildly elevated proteinuria. Estimated 24h protein = 0.45 × 1.5 = 0.675 g/day. ACR = (30/100) × 1000 = 300 mg/g, borderline A2/A3 (microalbuminuria-macroalbuminuria). In a diabetic patient, this warrants ACE inhibitor initiation and closer monitoring.
While spot PCR is adequate for screening and monitoring, a timed 24-hour collection remains the gold standard in specific situations: (1) significant discrepancy between spot PCR and clinical picture, (2) suspected overflow proteinuria (multiple myeloma — Bence Jones proteins may not react on standard dipstick), (3) extreme muscle mass or cachexia altering creatinine excretion, and (4) initial workup for nephrotic syndrome. The 24-hour collection also measures total creatinine excretion, useful for assessing collection completeness and estimating GFR.
SGLT2 inhibitors (dapagliflozin, empagliflozin, canagliflozin) represent the most significant advance in proteinuric kidney disease treatment in decades. The DAPA-CKD trial showed a 39% relative risk reduction in CKD progression with dapagliflozin, regardless of diabetes status. These drugs reduce proteinuria by 30–40% through tubuloglomerular feedback modulation, reducing intraglomerular pressure. They are now recommended as first-line therapy for proteinuric CKD by KDIGO guidelines.
In pregnancy, a PCR ≥ 0.3 g/g after 20 weeks gestation with new-onset hypertension suggests preeclampsia. The spot PCR has replaced 24-hour collection as the primary diagnostic tool in most obstetric guidelines due to faster turnaround. However, PCR can underestimate proteinuria in preeclampsia due to dilute urine from increased renal plasma flow — clinical judgment remains essential.
The correlation is approximately r = 0.93. Accuracy is highest for first-morning specimens. The main limitation is variation in creatinine excretion — muscular individuals produce more creatinine, potentially underestimating PCR. Despite this, most guidelines accept spot PCR as an adequate substitute for 24-hour collection.
PCR measures total protein (albumin + globulins + tubular proteins) relative to creatinine. ACR specifically measures albumin. ACR is more sensitive for early diabetic nephropathy (detects microalbuminuria at 30–300 mg/g). PCR is better for overall proteinuria assessment, including non-albumin proteinuria seen in tubular disease or multiple myeloma.
Any abnormal result should be confirmed with a repeat first-morning specimen 1–3 months later. Transient proteinuria (fever, strenuous exercise, UTI, dehydration) can cause false positives. Two abnormal results 3+ months apart define persistent proteinuria.
A PCR ≥ 3.5 g/g (or 24-hour protein ≥ 3.5 g). It indicates severe glomerular damage and is typically accompanied by hypoalbuminemia (<3.0 g/dL), peripheral edema, hyperlipidemia, and lipiduria — together constituting nephrotic syndrome. Common causes include minimal change disease, FSGS, membranous nephropathy, and diabetic nephropathy.
First-morning specimen is preferred because it eliminates the confounding effect of orthostatic (postural) proteinuria and reduces variability. If a first-morning specimen is not available, random urine is acceptable but may overestimate proteinuria if collected after prolonged standing or exercise.
Proteinuria is an independent risk factor for cardiovascular events and mortality, even at levels below the "abnormal" threshold. The PREVEND study showed that each doubling of urinary albumin excretion increases cardiovascular mortality by 29%. This relationship exists independent of GFR, blood pressure, and diabetes status.