Urine Urea Nitrogen Unit Converter

Convert urine urea nitrogen between mg/dL, mmol/L and g/L, and keep urea nitrogen and urea itself apart.

Last updated 2 Sep 2026

Urine Urea Nitrogen converter

Mass ⇄ molar

Urine urea nitrogen

Divide mmol/L by 0.357 to get mg/dL. Urea in mmol/L is half the urea-nitrogen figure in mmol/L.

321.3mmol/LExample

Urine urea nitrogen 900 mg/dL

Formula and conversion factor

mmol/L (urea nitrogen) = mg/dL × 0.357
mg/dL = mmol/L ÷ 0.357
g/L = mg/dL ÷ 100 · urea in mmol/L = urea nitrogen in mmol/L ÷ 2

0.357: derived from 28.014 g/mol, the mass of the two nitrogen atoms in one molecule of urea
÷ 2: each urea molecule carries two nitrogen atoms, so urea in mmol/L is half the urea-nitrogen figure in mmol/L
g/24 h: the 24-hour output needs the collection volume as well as the concentration; the concentration alone cannot give it

Worked example

Urine urea nitrogen 900 mg/dL
900 × 0.357 = 321.3 mmol/L of urea nitrogen
= 9.00 g/L
As urea rather than urea nitrogen, 321.3 ÷ 2 = 160.6 mmol/L

Urine urea nitrogen converted

The last column is urea itself, which is what laboratories outside the United States report. Confusing it with urea nitrogen doubles or halves the answer.
mg/dL	mmol/L (urea nitrogen)	g/L	mmol/L as urea
300	107.1	3.00	53.5
600	214.2	6.00	107.1
900	321.3	9.00	160.6
1,500	535.4	15.00	267.7

Concentration to 24-hour output

The same concentration gives very different daily outputs. Nitrogen balance needs the 24-hour figure, so the collection volume must be recorded.
24-hour volume	At 900 mg/dL	Urine urea nitrogen per 24 h
1.0 L	900 mg/dL = 9.00 g/L	9.0 g
1.5 L	900 mg/dL = 9.00 g/L	13.5 g
2.5 L	900 mg/dL = 9.00 g/L	22.5 g

Urea nitrogen is not urea, and concentration is not output

Urine urea nitrogen in mg/dL is converted to mmol/L by multiplying by 0.357, a factor derived from 28.014 g/mol — the mass of the two nitrogen atoms carried by one molecule of urea. Converting to g/L is simply a matter of dividing the mg/dL figure by 100, since 900 mg/dL is 9.00 g/L. The unit that appears on the report depends on the laboratory, and all three describe the same specimen.

The important distinction is that this is urea nitrogen, not urea. United States laboratories report the nitrogen content, as they do for blood urea nitrogen; laboratories elsewhere report urea itself in mmol/L. Urea in mmol/L is the urea-nitrogen figure in mmol/L divided by two, because each urea molecule carries two nitrogen atoms. A urine urea nitrogen of 321.3 mmol/L is therefore a urea of 160.6 mmol/L, and treating one as the other is a twofold error in whichever direction it is made.

The second trap is that a concentration is not an output. Converting mg/dL to grams per 24 hours needs the 24-hour collection volume, which the concentration alone does not supply: 900 mg/dL is 9.0 g of urea nitrogen in a litre, 13.5 g in 1.5 litres and 22.5 g in 2.5 litres. A concentrated sample from a dehydrated patient and a dilute one from a well-hydrated patient can represent the same daily excretion, so the volume must be recorded with the specimen.

Urine urea nitrogen matters clinically for two reasons. It underpins the nitrogen balance calculation, in which the 24-hour output is subtracted from nitrogen intake along with a constant for insensible losses — and because that calculation uses the 24-hour figure, an incomplete collection makes the balance look better than it is. It is also used in the urea-to-creatinine ratio on the same collection to assess whether a 24-hour collection is adequate, alongside total creatinine, which is the more established check.

Frequently asked questions

How do I convert urine urea nitrogen from mg/dL to mmol/L?

Multiply by 0.357, a factor derived from 28.014 g/mol, the mass of the two nitrogen atoms in one urea molecule. A urine urea nitrogen of 900 mg/dL is 321.3 mmol/L.

What is the difference between urea nitrogen and urea?

Urea nitrogen reports only the nitrogen content of urea. Each urea molecule carries two nitrogen atoms, so urea in mmol/L is the urea-nitrogen figure in mmol/L divided by two. A urea nitrogen of 321.3 mmol/L is a urea of 160.6 mmol/L.

How do I get grams per 24 hours from a concentration?

Multiply the concentration in g/L by the 24-hour urine volume in litres. The concentration alone cannot give the daily output — 900 mg/dL is 9.0 g in a litre but 13.5 g in 1.5 litres.

Why is urine urea nitrogen measured?

Mainly to calculate nitrogen balance, where the 24-hour output stands for nitrogen loss. It is also used in the urea-to-creatinine ratio on the same collection when assessing whether a 24-hour collection is adequate.

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References

Burtis CA, Ashwood ER, Bruns DE, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018.
Singer P, Blaser AR, Berger MM, et al. ESPEN practical and partially revised guideline: clinical nutrition in the intensive care unit. Clin Nutr. 2023;42(9):1671–1689.