Updated June 2026 · For clinical use by qualified healthcare professionals
UPCR Calculator — Spot Urine Protein:Creatinine
mg/dL · g/L + mmol/L · Auto KDIGO classification
UPCR Interpretation — KDIGO Reference Table
UPCR (mg/mg) numerically approximates 24-hour urinary protein excretion in grams per day. Multiply by 1000 to express as mg/g. Use this table alongside the calculator above to classify the result.
| UPCR (mg/mg) | UPCR (mg/g) | Category | Est. 24h Protein | Clinical Significance |
|---|---|---|---|---|
| <0.15 | <150 | A1 Normal | <150 mg/day | Normal — expected in healthy adults |
| 0.15–0.5 | 150–500 | A2 Mild | 150–500 mg/day | Moderately elevated — CKD/diabetes/hypertension workup |
| 0.5–3.5 | 500–3500 | A3 Moderate–Severe | 500–3500 mg/day | Significant proteinuria — nephrology referral |
| >3.5 | >3500 | Nephrotic Range | >3500 mg/day | Nephrotic syndrome workup — urgent nephrology |
UPCR — Clinical Reference Guide
What is UPCR (Urine Protein-to-Creatinine Ratio)?
The urine protein-to-creatinine ratio (UPCR), also written as PCR or urine PCR, estimates total 24-hour urinary protein excretion from a single spot urine sample. Because creatinine excretion is relatively constant throughout the day, dividing urine protein by urine creatinine corrects for variations in urine concentration — eliminating the need for an inconvenient and often inaccurate 24-hour urine collection. UPCR (mg/mg) is numerically equivalent to grams of protein excreted per gram of creatinine, and closely approximates 24-hour proteinuria in g/day.
UPCR Formula
UPCR (mg/mg) = Urine Protein (mg/dL) ÷ Urine Creatinine (mg/dL)
To express the result in mg/g, multiply by 1000. If your lab reports protein in g/L and creatinine in mmol/L, the calculator above converts these to standard units automatically using the relationship 1 mmol/L creatinine = 11.312 mg/dL.
Why UPCR Instead of 24-Hour Urine Collection?
24-hour urine collection is inconvenient for patients and frequently inaccurate due to incomplete or improperly timed collection. UPCR from a spot urine specimen — ideally a first morning void to avoid postural (orthostatic) proteinuria — correlates well with 24-hour urinary protein excretion (r >0.9 in most studies). KDIGO 2012 guidelines recommend UPCR or ACR (albumin-creatinine ratio) as the standard for proteinuria quantification in chronic kidney disease.
Causes of Elevated UPCR
- Glomerular proteinuria: Diabetic nephropathy, IgA nephropathy, membranous nephropathy, FSGS, lupus nephritis, amyloidosis — typically high UPCR, may reach nephrotic range
- Tubular proteinuria: Acute kidney injury, Fanconi syndrome, heavy metal toxicity — low molecular weight proteins, UPCR typically <1.5
- Overflow proteinuria: Multiple myeloma (Bence-Jones proteins), haemoglobinuria, myoglobinuria — standard urine dipstick may miss Bence-Jones protein
- Transient or benign: Fever, vigorous exercise, orthostatic (postural) proteinuria — check a first morning void sample to exclude this
UPCR vs UACR — Which Test to Use
| Feature | UPCR | UACR |
|---|---|---|
| What it measures | All urinary proteins | Albumin only |
| Best for | Non-diabetic CKD, known heavy proteinuria | Diabetic nephropathy, early CKD risk |
| Detects microalbuminuria | ✗ | ✓ (>30 mg/g) |
| Preferred by KDIGO for CKD staging | ✓ Either acceptable | ✓ Either acceptable |
| Detects tubular/overflow proteinuria | ✓ | ✗ |
Sources of Error in UPCR
False high UPCR: blood contamination (menstruation, haematuria), urinary tract infection (Tamm-Horsfall protein, pyuria), very concentrated urine. False low UPCR: very dilute urine from high fluid intake. Postural (orthostatic) proteinuria is common in adolescents — UPCR is elevated when upright but normal on a recumbent first morning void sample. Bence-Jones proteinuria in multiple myeloma is often missed by standard urine dipstick and requires urine protein electrophoresis (UPEP) for detection.
UPCR in CKD Staging — KDIGO 2024
KDIGO 2024 CKD classification combines an albuminuria category (A1/A2/A3) with the eGFR stage (G1–G5) to assess prognosis. UACR <30 mg/g = A1 (normal/mild). UACR 30–300 mg/g = A2 (moderately increased). UACR >300 mg/g = A3 (severely increased). A worsening albuminuria category indicates CKD progression and should prompt nephrology referral and treatment escalation.
Managing Proteinuria in CKD
First-line: ACE inhibitors (ramipril, enalapril) or ARBs (losartan, telmisartan) reduce intraglomerular pressure and proteinuria by 30–50%, slowing CKD progression. Target blood pressure <130/80 mmHg. SGLT2 inhibitors (empagliflozin, dapagliflozin) provide additional renoprotection in proteinuric CKD independent of diabetes status. Finerenone, a mineralocorticoid receptor antagonist, further reduces CKD progression in type 2 diabetes with UACR ≥30 mg/g. NSAIDs, nephrotoxic drugs, and iodinated contrast should be avoided in proteinuric CKD wherever possible.
Frequently Asked Questions
What is the urine protein-to-creatinine ratio?
The urine protein-to-creatinine ratio (UPCR) estimates 24-hour urine protein excretion from a spot urine sample. UPCR (mg/mg) numerically approximates 24-hour proteinuria in g/day. UPCR below 0.15 mg/mg is normal; 0.15–3.5 indicates significant proteinuria; above 3.5 mg/mg is nephrotic-range proteinuria.
How do you calculate UPCR?
UPCR = Urine Protein (mg/dL) ÷ Urine Creatinine (mg/dL). Enter both values from the same spot urine sample in the calculator above. Multiply the result by 1000 to express it as mg/g instead of mg/mg.
What is a normal UPCR value?
A normal urine protein-to-creatinine ratio is below 0.15 mg/mg (below 150 mg/g). Some labs use an upper limit of 0.2 mg/mg (200 mg/g) — check the reference range on your specific lab report, as cutoffs can vary slightly between laboratories.
Why is UPCR preferred over 24-hour urine collection?
24-hour urine collection is inconvenient and often inaccurately collected, which delays diagnosis. UPCR from a spot sample — preferably a first morning void — correlates closely with 24-hour proteinuria and is reproducible. KDIGO guidelines recommend it as the standard method for proteinuria quantification in CKD monitoring.
What does nephrotic-range proteinuria mean?
UPCR greater than 3.5 mg/mg (equivalent to more than 3.5 g/day proteinuria) defines nephrotic-range proteinuria. When accompanied by hypoalbuminaemia (<3.5 g/dL), oedema, and hyperlipidaemia, this defines nephrotic syndrome. Common causes include membranous nephropathy, minimal change disease, FSGS, diabetic nephropathy, and amyloidosis.
What is the difference between UPCR and ACR (albumin-creatinine ratio)?
UPCR measures total urinary protein and is preferred for general proteinuria quantification, non-diabetic CKD, and monitoring known heavy proteinuria. ACR measures only albumin and is preferred for diabetic nephropathy screening and cardiovascular risk assessment, since it detects early microalbuminuria (>30 mg/g) that UPCR may miss.
What causes a falsely high or low UPCR result?
False high results can occur with blood contamination, urinary tract infection, or very concentrated urine. False low results occur with very dilute urine from high fluid intake. Postural proteinuria, common in adolescents, causes an elevated UPCR when upright but a normal result on a first morning void sample.