These calculators covert creatinine and urea or blood urea nitrogen (BUN) from intenational units to American units and vice versa. The urea tool converts urea in mmol/l to or from BUN in mg/dl.
Urea can also be expressed as mg/dl although it is not common to do so. Although this tool does not convert urea to mg/dl, the conversion from BUN to urea can be done manually using this formula:
$$urea_{mg/dl} = BUN_{mg/dl} \times 2.14$$