Browse Medical Laboratory Calculators
Urea & BUN Converter
Urea is the principal waste product of protein metabolism, synthesized in the liver via the urea cycle and excreted by the kidneys. It is a key marker for kidney function and hydration status.
There is a significant difference in reporting units globally. In the United States, laboratories report the mass of the nitrogen content only, known as Blood Urea Nitrogen (BUN). In most other countries (SI units), the measurement reflects the Whole Urea Molecule. This converter standardizes these results.
BUN (Nitrogen)
US StandardBlood Urea Nitrogen. Mass of Nitrogen only.
Urea (Molecule)
Measurement of the whole Urea molecule (SI).
Clinical Context
Reference Ranges:
• BUN (US): 7 – 20 mg/dL.
• Urea (SI): 2.5 – 7.1 mmol/L.
Conversion Logic:
Molecular Weight of Urea (CO(NH2)2) = 60.06 g/mol.
Atomic Weight of Nitrogen (N2) = 28.014 g/mol.
1 mg/dL BUN ≈ 0.357 mmol/L Urea.
1 mmol/L Urea ≈ 2.8 mg/dL BUN.
Clinical References
How to Use This Converter
Follow these steps to normalize Urea/BUN values.
Identify the Unit
Check if your lab report says BUN (mg/dL) or Urea (mmol/L).
Enter Values
Input the numeric value into the corresponding field.
Automatic Calculation
The tool calculates the equivalent. Use the factor 2.8 for mental math (1 mmol/L Urea = 2.8 mg/dL BUN).
Frequently Asked Questions
Chemically no, but clinically they measure the same waste product. BUN measures just the nitrogen part, while Urea measures the whole molecule. The ratio is roughly 1:2.14 by weight.
High BUN (Azotemia) can be caused by kidney dysfunction, dehydration, high protein diet, or GI bleeding.