Free Water Deficit in Hypernatremia & Safe 0.5 mEq/L/hr Correction Calculator

Compute Free Water Deficit = TBW × ((Na / 140) − 1) and safe hourly replacement rate.

Total Free Water Deficit
5.79 Liters
Estimated Total Body Water (TBW) 45 Liters
Safe Correction Time (@ 0.5 mEq/L/hr) 36 hours
Free Water Infusion Rate (Excl. Insensible) 160.71 mL/hr
Inputs
⚡ Scenarios:
kg
Patient body weight in kilograms.
fraction
Total Body Water (TBW) fraction (0.60 adult male, 0.50 adult female/elderly).
mEq/L
Current hypernatremic serum sodium (mEq/L).
mEq/L
Target normonatremic serum sodium (typically 140 mEq/L).
Results & Graph
Total Free Water Deficit
5.79 Liters
Estimated Total Body Water (TBW)
45 Liters
Safe Correction Time (@ 0.5 mEq/L/hr)
36 hours
Free Water Infusion Rate (Excl. Insensible)
160.71 mL/hr

Total Free Water Deficit

Graph 1 • Free Water Deficit • Domain Architecture & Live Telemetry Maps Patient Weight Kg, Total Body Water Fraction, Current Serum Sodium Meq L through Free Water Deficit Formula.
Free Water Deficit • Clinical & Physiological Reference Scale Low / Baseline Target / Reference Elevated / Watch High / Action Total Free Water Deficit: 5.79 Liters Estimated Total Body Water 45 Liters Safe Correction Time (@ 0. 36 hours Free Water Infusion Rate ( 160.71 mL/hr
Graph 2 • Total Free Water Deficit Across Patient Weight Kg Sweep (40% → 160%) Evaluates TBW = Weight_kg × WaterFraction; FreeWaterDeficit_L = TBW × [ (Measure across 7 operating points (current input highlighted).
0 Liters 5.09 Liters 10.19 Liters 2.31 30kg 3.47 45kg 4.63 60kg 5.79 75kg 6.94 90kg 8.10 105kg 9.26 120kg
Graph 3 • Joint Sensitivity: Patient Weight Kg × Total Body Water Fraction Compares Total Free Water Deficit when Total Body Water Fraction is shifted +25% (solid) vs. −25% (dashed).
0 Liters 5.17 Liters 10.34 Liters --- Total Body Water Fraction @ 75% 5.06 -30% 6.15 -15% 7.23 +0% 8.32 +15% 9.40 +30%
Summary: Lowering Na+ from 158 to 140 mEq/L (TBW = 45 L) requires 5.79 L (5786 mL) of free water over 36 hours (~161 mL/hr at 0.5 mEq/L/hr).
Summary: Lowering Na+ from 158 to 140 mEq/L (TBW = 45 L) requires 5.79 L (5786 mL) of free water over 36 hours (~161 mL/hr at 0.5 mEq/L/hr).
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Interactive chart & math engine powered by CalculatorGraph

Formula & Mathematical Methodology: Free Water Deficit Formula

TBW = Weightkg × WaterFraction
FreeWaterDeficitL = TBW × [ (MeasuredNa / TargetNa) − 1 ]
TBW = Weight_kg × WaterFraction; FreeWaterDeficit_L = TBW × [ (Measured_Na / Target_Na) − 1 ]
  • patientWeightKg: Patient Weight Kg (kg)
  • totalBodyWaterFraction: Total Body Water Fraction (fraction)
  • currentSerumSodiumMeqL: Current Serum Sodium Meq L (mEq/L)
  • targetSerumSodiumMeqL: Target Serum Sodium Meq L (mEq/L)

Rounding: Clinical scores round to statutory integer or decimal precision; physiological metrics round to 2 decimal places.

Worked Example: Clinical / Physiology Scenario: Free Water Deficit

Compute Free Water Deficit = TBW × ((Na / 140) − 1) and safe hourly replacement rate.

  1. Enter lab values, anthropometric measurements, or performance test metrics.
  2. Evaluate the reference equation: TBW = Weight_kg × WaterFraction; FreeWaterDeficit_L = TBW × [ (Measured_Na / Target_Na) − 1 ].
  3. Inspect the primary classification, supporting indices, and 3 SVG charts.
Result: Computes Free Water Deficit via TBW = Weight_kg × WaterFraction; FreeWaterDeficit_L = TBW × [ (Measured_Na / Target_Na) − 1 ].

Frequently Asked Questions

How does the Free Water Deficit in Hypernatremia & Safe 0.5 mEq/L/hr Correction Calculator compute its result?

It evaluates TBW = Weight_kg × WaterFraction; FreeWaterDeficit_L = TBW × [ (Measured_Na / Target_Na) − 1 ] directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to solve backwards for a target lab value or pace?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any numeric input parameter.

Are my health and biometric inputs kept private?

Yes. All calculations run 100% locally on your device with zero external transmission.

Health & Fitness · Clinical Nephrology & Electrolytes

Free Water Deficit in Hypernatremia & Safe 0.5 mEq/L/hr Correction Calculator: inputs, method, and how to read the result

Compute Free Water Deficit = TBW × ((Na / 140) − 1) and safe hourly replacement rate.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Patient Weight Kg: Patient body weight in kilograms.
  • Total Body Water Fraction: Total Body Water (TBW) fraction (0.60 adult male, 0.50 adult female/elderly).
  • Current Serum Sodium Meq L: Current hypernatremic serum sodium (mEq/L).
  • Target Serum Sodium Meq L: Target normonatremic serum sodium (typically 140 mEq/L).

What the calculation includes

With the default values shown, Total Free Water Deficit is 5.79 Liters. The calculation follows Free Water Deficit Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Patient Weight Kg from 75 kg to 83 kg changes Total Free Water Deficit from 5.79 Liters to 6.4 Liters. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses peer-reviewed clinical and sports physiology formulas.
  • For educational and informational reference only; clinical scores do not replace physician judgment or laboratory reference ranges.

Scope: Global Clinical & Sports Science Consensus Check the assumptions and limitations against your situation before relying on the estimate.

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