FENa Calculator

Why use an online FENA calculator?

MYcalcu’s FENA calculator (fractional extraction of sodium calculator) is highly useful in the evaluation of kidney failure and even low urine output.

This online calculator even enables you to find out the cause of kidney failure as well.

It has no log-in or payment restrictions, and it is totally free tool.

How does it work?

Following is the formula used by Mycalcu’s calculator.

Fractional Excretion of Sodium (FENa) = (PCr * UNa) / (PNa * UCr)


  • PCr stands for plasma creatinine.
  • PNa stands for plasma sodium.
  • UCR stands for urine creatinine.
  • UNa stands for urine sodium.

Interpretation of results

Prerenal cause: FENa <1%

Intrinsic Renal cause: FENa 1-4%

Postrenal cause: FENa >4%

How to use the FENA calculator?

Enter the required data in the provided fields and then click calculate.