BUN and urea conversion: mg/dL to mmol/L

For urea, 1 mg/dL BUN = 0.356964 mmol/L, and 1 mmol/L = 2.8014 mg/dL BUN.

Common values

mg/dL BUN to mmol/L

Urea and BUN, mg/dL BUN to mmol/L
mg/dL BUN	mmol/L
5	1.8
7	2.5
10	3.6
14	5.0
20	7.1
25	8.9
30	10.7
40	14.3
50	17.8
80	28.6
100	35.7

mmol/L to mg/dL BUN

Urea and BUN, mmol/L to mg/dL BUN
mmol/L	mg/dL BUN
2	6
2.5	7
3	8
4	11
5	14
6	17
7	20
8	22
10	28
15	42
20	56
30	84

mg/dL BUN to mg/dL urea

Urea and BUN, mg/dL BUN to mg/dL urea
mg/dL BUN	mg/dL urea
5	11
7	15
10	21
14	30
20	43
25	54
30	64
40	86
50	107
80	172
100	214

mg/dL urea to mmol/L

Urea and BUN, mg/dL urea to mmol/L
mg/dL urea	mmol/L
10	1.7
15	2.5
20	3.3
30	5.0
40	6.7
45	7.5
50	8.3
60	10.0
80	13.3
100	16.7
150	25.0
200	33.3

Each converted value is worked out in full and then rounded: mmol/L to one decimal place; mg/dL BUN and mg/dL urea to whole numbers.

Source: molar masses summed from the IUPAC CIAAW abridged standard atomic weights, 2024.

A study tool, not a clinical one

This page exists for converting urea between mg/dL BUN and mmol/L, and learning where the factor between the two units comes from. It is not clinical decision support and must not be used to treat anybody.

Read a result against its own report. Laboratories differ in method and in the population they set reference intervals from, so interpret a converted number against the ranges printed on the report it came from.
The factor belongs to urea. Applied to any other analyte, it gives a number that looks just as plausible and is wrong.
Every calculation here is shown, not hidden. If a step does not match what you were taught, follow the working rather than the output, and tell us if we have it wrong. How the pages are checked is set out in the editorial policy.

Why BUN and urea have different factors

BUN, blood urea nitrogen, is the mass of the nitrogen in the urea rather than of the urea. Each molecule of urea, CH₄N₂O, carries two nitrogen atoms, 2 × 14.007 = 28.014 g per mole of urea, so 1 mg/dL BUN = 10 ÷ 28.014 = 0.356964 mmol/L of urea. Urea itself is 60.056 g/mol, so 1 mg/dL of urea is 10 ÷ 60.056 = 0.166511 mmol/L.

Urea in mg/dL is BUN × 60.056 ÷ 28.014, about 2.14 times the BUN, so a BUN of 14 mg/dL is a urea of 30 mg/dL.

mmol/L = mg/dL BUN × 10 ÷ 28.014
mg/dL BUN = mmol/L × 28.014 ÷ 10
mg/dL urea = mg/dL BUN × 60.056 ÷ 28.014
mmol/L = mg/dL urea × 10 ÷ 60.056

Which countries report which unit

American laboratories usually report blood urea nitrogen, BUN, in mg/dL, and most Indian ones report blood urea, the whole molecule, in mg/dL. British, Canadian and Australian laboratories report urea in mmol/L.