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Estimates maintenance fluid requirement based on body weight.
Fluid requirement = 35 mL/kg/day
~2,000–3,000 mL/day for average adults
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.
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:
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.