STAR TOPIC · HEALTH · KIDNEY TESTS
Educational tool only — not a diagnosis. A spot urine protein-creatinine ratio (UPCR) estimates how much protein the kidneys are leaking, without a 24-hour urine collection. At the defaults — protein 30 mg/dL and creatinine 100 mg/dL — the ratio is 0.30 mg/mg (300 mg/g), in the abnormal proteinuria range. Enter your lab values below, then discuss the result with a clinician: this calculator cannot diagnose kidney disease or replace medical advice.
Educational only — not a diagnosis, and not a substitute for a clinician. UPCR divides urine protein by urine creatinine from the same spot sample, so dilution cancels out. Both values can be entered in mg/dL or g/L (1 g/L = 100 mg/dL); the calculator converts to mg/dL before dividing. Categories used here: below 0.20 normal, 0.20 to 3.50 abnormal proteinuria, above 3.50 nephrotic-range.
This calculator is educational only. It does not diagnose kidney disease, and no result here should change treatment or prompt worry on its own — discuss every result with a clinician. With that said, the defaults tell a clear story: protein 30 mg/dL over creatinine 100 mg/dL gives 0.30 mg/mg, or 300 mg/g, which sits in the abnormal proteinuria range (0.20–3.50). It is mildly raised, not nephrotic: the nephrotic threshold of 3.50 is more than ten times higher. A single spot result like this is a reason for a repeat test and a clinical conversation, not a conclusion.
Setup: urine protein 30 mg/dL, urine creatinine 100 mg/dL.
Line 1 — the ratio. 30 ÷ 100 = 0.30 mg/mg. Because both values are in mg/dL, the units cancel, and mg/mg is numerically the same as g/g.
Line 2 — mg/g. 0.30 × 1,000 = 300 mg/g, the form many labs and guidelines quote.
Line 3 — estimated 24-hour excretion. The ratio approximates grams of protein per day, so 0.30 corresponds to about 0.30 g/day — an estimate, not a measurement.
Line 4 — the category. 0.30 falls between 0.20 and 3.50, so the category is abnormal proteinuria.
Protein 10 mg/dL over creatinine 100 mg/dL gives 0.10 mg/mg (100 mg/g), about 0.10 g/day — below the 0.20 threshold, so normal by this test. Small day-to-day variation is expected; a single normal spot result does not rule out kidney disease when other signs are present, which is why clinicians repeat tests and check blood work alongside.
Protein 400 mg/dL over creatinine 100 mg/dL gives 4.00 mg/mg (4,000 mg/g), about 4.00 g/day — above the 3.50 threshold, so nephrotic-range. Results in this range are typically taken to a clinician promptly, because heavy protein loss of this size usually needs investigation and often treatment, and it can come with swelling and low blood protein.
Units trip people up more than math does: protein 0.30 g/L is the same as 30 mg/dL, and entering 0.30 while the unit is set to mg/dL would wrongly give 0.003. Always match the unit on your lab report. Dilution is the other trap: when creatinine falls below about 20 mg/dL, the urine is very dilute and the ratio becomes unstable — the calculator flags this, and the right move is a repeat sample, not a conclusion. Muscle mass also shifts creatinine, so a muscular person and a frail person with the same kidney function can have different ratios from the same protein level.
A 24-hour urine collection measures protein directly, but collecting every drop for a day is error-prone — one missed sample ruins it. The spot ratio works because creatinine is excreted at a fairly steady rate over the day, so dividing by creatinine corrects for how concentrated or dilute that one sample happens to be. Studies find the spot ratio tracks the 24-hour result closely enough for screening and monitoring, which is why it has largely replaced the jug in routine care. It remains an approximation: it does not replace a 24-hour collection when precision matters, and it varies with hydration, exercise, fever, and muscle mass.
| Output | Formula | What it means |
|---|---|---|
| UPCR (mg/mg) | protein ÷ creatinine, both in mg/dL | 0.30 at the defaults — the ratio itself, unit-free. |
| UPCR (mg/g) | ratio × 1,000 | 300 mg/g at the defaults — the form many labs report. |
| Estimated 24-hour protein | ≈ ratio, in g/day | About 0.30 g/day at the defaults — an estimate, not a measurement. |
| Category | < 0.20 / 0.20–3.50 / > 3.50 | Abnormal proteinuria at the defaults — mildly raised, not nephrotic. |
The ratio is exact arithmetic on the values entered, but the clinical meaning is approximate: a spot UPCR estimates 24-hour excretion and does not replace a 24-hour collection, especially when precision changes treatment. It varies with hydration, muscle mass, exercise, fever, and urinary tract infection, and a creatinine below 20 mg/dL signals very dilute urine that makes the ratio unreliable. Category thresholds of 0.20 and 3.50 are the widely used clinical cutoffs; individual labs and guidelines vary, and your clinician interprets results against your full history. Educational only — not a diagnosis, not medical advice; discuss any result with a clinician. Error policy: a zero or negative creatinine, a negative protein, or values above 5,000 mg/dL protein or 3,000 mg/dL creatinine are reported as errors rather than modeled.
Bright Side Kit. "Protein-Creatinine Ratio Calculator: UPCR & Kidney Test." https://brightoolbox.com/protein-creatinine-ratio-calculator/ Accessed October 24, 2026.Data sourcesBelow 0.20 mg/mg (200 mg/g). Results from 0.20 to 3.50 indicate abnormal proteinuria, and results above 3.50 are in the nephrotic range. Thresholds vary slightly by lab and guideline, so your clinician interprets your result against your full history.
300 mg/g, in the abnormal proteinuria range. It corresponds to roughly 0.30 grams of protein lost per day — mildly raised, not nephrotic, and usually a reason for a repeat test and a clinical conversation rather than alarm. This is educational information, not a diagnosis.
Above 3.50 mg/mg (3,500 mg/g). That corresponds to more than about 3.5 grams of protein per day, heavy loss that typically needs prompt clinical investigation. A result in this range should be taken to a clinician promptly.
No — UPCR estimates it. The spot ratio divides one sample’s protein by its creatinine, which corrects for dilution and tracks the 24-hour total closely enough for screening and monitoring. When precision matters, a clinician may still order a full 24-hour collection.
Divide by 1,000. A lab value of 300 mg/g is 0.30 mg/mg, and 4,000 mg/g is 4.00 mg/mg. The mg/mg figure is also numerically the same as g/g, and roughly the same as grams per day of protein excretion.
Because division by zero is undefined. A zero creatinine means the sample has no measurable creatinine, which usually means a lab or entry error — check the report and re-enter. A very low creatinine (below 20 mg/dL) is flagged separately as very dilute urine.
Yes, both can shift a spot result. Strenuous exercise, fever, dehydration, and urinary tract infection can all raise urine protein temporarily. That is why an abnormal spot result is usually repeated, often with a first-morning sample, before any conclusion is drawn.
Yes. Creatinine comes from muscle, so a very muscular person produces more of it and a frail person less, which shifts the ratio even when kidney protein loss is the same. Clinicians read UPCR alongside body size, blood creatinine, and other markers for this reason.