The protein/creatinine ratio (PCR) is a same-unit comparison of urine protein to urine creatinine from a single spot sample that approximates 24-hour urine protein excretion without requiring a timed collection. This calculator computes the ratio and classifies it against normal, proteinuria, and nephrotic-range bands.

How the protein/creatinine ratio works

PCR is simply urine protein divided by urine creatinine, both measured in mg/dL on the same spot sample: PCR = protein ÷ creatinine. Because the units cancel, the resulting ratio in g/g closely approximates 24-hour urine protein excretion in grams per day, since creatinine excretion is relatively constant across the day for a given person.

A normal PCR is below 0.2 g/g. Values from 0.2 up to 3.5 g/g indicate proteinuria, and a PCR at or above 3.5 g/g is considered nephrotic-range, the threshold historically associated with nephrotic syndrome.

Inputs and what they mean

Urine protein (mg/dL) is the total protein concentration measured in a spot urine sample. Urine creatinine (mg/dL) is the creatinine concentration in that same sample, used as an internal reference because creatinine excretion is fairly stable throughout the day.

Both values must come from the same specimen — mixing protein from one sample with creatinine from another produces a meaningless ratio.

Limits and edge cases

PCR is a screening and estimation tool, not a diagnosis. Very dilute urine (for example, after high fluid intake) or very concentrated urine (for example, dehydration) can shift the ratio away from the true 24-hour value even though the underlying protein excretion hasn't changed. PCR also does not distinguish glomerular from tubular proteinuria the way the albumin/creatinine ratio (ACR) can. A single elevated PCR should prompt confirmation — either a repeat spot sample or a 24-hour urine collection — rather than an immediate diagnosis.