Fractional Excretion of Sodium (FENa) Calculator

mmol/L
mmol/L
mg/dL
mg/dL
Health Updated 14 Jun 2026

Fractional Excretion of Sodium (FENa) Calculator is a health and wellness calculator that helps you calculate fractional excretion of sodium (fena) values from your input data. The formula used is: FENa = (urine Na × plasma Cr) ÷ (plasma Na × urine Cr) × 100. Enter values using the units shown next to each input field (e.g. kg, cm, years).

Rates and fees change frequently. Always confirm the current figures with the official authority before relying on this result.
  • Diagnostic aid for AKI. Requires physician interpretation; invalid with diuretics.

Formula

FENa = (urine Na × plasma Cr) ÷ (plasma Na × urine Cr) × 100
  • Fractional Excretion of Sodium (FENa) Calculator gives you a fast estimate using your inputs and updates instantly when you change any value.
  • Formula: FENa = (urine Na × plasma Cr) ÷ (plasma Na × urine Cr) × 100
  • Input definitions: • Urine sodium: the numeric urine sodium used in the calculation • Plasma sodium: the numeric plasma sodium used in the calculation • Urine creatinine: the numeric urine creatinine used in the calculation • Plasma creatinine: the numeric plasma creatinine used in the calculation
  • Manual method: write down each input, apply the formula step by step, then compare your manual result with the calculator output.
  • Enter values using the units shown next to each input field (e.g. kg, cm, years).
  • This calculator uses widely accepted health formulas and returns screening estimates only. It does not replace a diagnosis from a qualified healthcare professional.
  • Compare your result with published reference ranges. Values outside the normal range warrant a conversation with your doctor.
  • Practical tip: test a low, medium, and high scenario to understand sensitivity before making decisions.

Example Calculation

Inputs
  • Urine sodium: 20 mmol/L
  • Plasma sodium: 140 mmol/L
  • Urine creatinine: 100 mg/dL
  • Plasma creatinine: 2 mg/dL

Suppose you enter: Urine sodium = 20, Plasma sodium = 140, Urine creatinine = 100, Plasma creatinine = 2.0. The calculator applies the formula (FENa = (urine Na × plasma Cr) ÷ (plasma Na × urine Cr) × 100) and shows all output values below. Change any input field to immediately see how the result changes.

Frequently asked questions

What is the Fractional Excretion of Sodium (FENa)?
The Fractional Excretion of Sodium (FENa) Calculator is a health and wellness calculator that helps you calculate fractional excretion of sodium (fena) values from your input data. Enter values using the units shown next to each input field (e.g. kg, cm, years).
When should I use this calculator?
Use this calculator whenever you need a quick, accurate result for fractional excretion of sodium (fena) values from your input data without working through the arithmetic manually.
What units should I enter?
Enter values using the units shown next to each input field (e.g. kg, cm, years).
How accurate are the results?
This calculator uses widely accepted health formulas and returns screening estimates only. It does not replace a diagnosis from a qualified healthcare professional.
How do I interpret the result?
Compare your result with published reference ranges. Values outside the normal range warrant a conversation with your doctor.
How can I verify the calculation manually?
Use the displayed formula and work through the numbers step by step. If your manual result differs slightly, check rounding and unit conversions first.
Can I use this for planning and budgeting?
Yes. Run best-case, expected, and worst-case inputs to compare outcomes and make safer planning decisions.

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