How to Use Free Water Deficit Calculator
- Enter body weight in kilograms.
- Choose mild, moderate, or severe dehydration. The calculator maps these to approximate deficit percentages.
- Enter age and sex so the estimate can be adjusted for typical differences in body water distribution.
Formula & Theory - Free Water Deficit Calculator
Free Water Deficit Calculator uses this core formula:
Water deficit ≈ Weight × Dehydration percentage × Age/sex adjustment factorThis calculator uses a practical dehydration-percentage model rather than a sodium-based hypernatremia formula. Mild, moderate, and severe categories are converted into approximate fractions of body weight, then adjusted for age and sex. The result is a fluid deficit estimate in liters. Real rehydration plans must consider sodium level, ongoing losses, heart or kidney disease, route of replacement, and how quickly the deficit developed.
Use Cases for Free Water Deficit Calculator
- Estimating fluid needs during dehydration triage or education.
- Comparing how mild, moderate, and severe dehydration change the liter estimate.
- Preparing a discussion about oral versus IV replacement while avoiding exact prescription claims.