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Estimates maintenance fluid requirement based on body weight.
Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.
This simple rule is often used for maintenance fluid planning.
Specialty
Internal MedicineCategory
Internal MedicineDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-07
Formula
Keywords
Normal Range
~2,000–3,000 mL/day for average adults
| Classification | Range |
|---|---|
Adults | 35 mL/kg/day |
Estimates a simple daily maintenance fluid requirement using a fixed 35 mL/kg/day rule based on body weight.
Estimated daily fluid requirement = weight (kg) x 35 mL/kg/day.
Body weight in kilograms, multiplied by 35 mL/kg/day.
The result approximates daily maintenance fluid needs at 35 mL/kg/day. For a 70 kg adult this is 2,450 mL/day (~2.5 L), consistent with typical adult maintenance estimates.
Simple weight-based rules give clinicians a rapid baseline for maintenance fluid planning, helping avoid both under- and over-hydration in routine care.
A 70 kg adult requires an estimate of daily maintenance fluid.
Inputs:
Expected Result: Fluid requirement = 70 × 35 = 2,450 mL/day (~2.5 L).
It is a common adult approximation for daily maintenance water needs. The Maintenance Fluids calculator uses the more granular 100/50/20 weight-based rule.
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. Fluid management must account for the individual's clinical status, losses, and comorbidities.