Fluid Deficit Calculator
Estimated fluid deficit from weight and dehydration percent
Equation & limitations
- Equation
- Deficit (L) = weight (kg) × dehydration (%) / 100
- Version
- Site-defined arithmetic (standard clinical estimation rule)
- Source
- Defined by Pharmapedia for this tool; reflects the common clinical deficit-estimation rule.
- Appropriate in
- Estimating pre-existing deficit when clinical dehydration has been assessed; the % is a clinical judgement, not a measurement.
- Limitations
- Covers only the pre-existing deficit — maintenance and ongoing losses are separate and must be added by a clinician.
- The dehydration % itself is an assessment, not an output of this tool.
- Fluid type, route, rate and monitoring (especially in children) are clinical decisions this tool does not make.
For educational use. Results support, and do not replace, clinical judgement — check them against the patient and local guidelines.