Free Water Deficit Calculator 2025

Calculate the water deficit in hypernatremia patients based on current sodium levels

Patient Data

Results

Enter patient data and click “Calculate” to see results.

About Free Water Deficit

The free water deficit calculation estimates the amount of water needed to correct hypernatremia. It’s based on the formula:

FWD = TBW × (Current Na/Target Na – 1)

Where TBW (Total Body Water) is estimated as:

  • Male: Weight (kg) × 0.6
  • Female: Weight (kg) × 0.5

Note: This calculator is for educational purposes only. Always consult clinical guidelines and consider patient-specific factors when making treatment decisions.