Renal Failure Index Calculator

Calculate the renal failure index to help distinguish prerenal from intrinsic acute kidney injury.

Aug 31, 2026 Renal #aki #rfi #renal-failure-index

Calculate

All fields required unless noted

Urine sodium (mEq/L)

Serum creatinine (mg/dL)

Urine creatinine (mg/dL)

Calculating...

Enter your values and press Calculate to see the result.

Formula & Clinical Notes

Formula

RFI = (UNa × SCr) / UCr

Clinical Notes

Like FENa, the renal failure index (RFI) compares urinary sodium excretion to renal concentrating ability. An RFI below 1 suggests prerenal azotemia; above 1 suggests intrinsic acute tubular necrosis. It is subject to the same limitations as FENa with diuretic use.

Sources

StatPearls — Renal Function Tests