Maintenance Fluid Rate Calculator

How to calculate maintenance fluid?

The 4-2-1 rule is the clinical standard for calculating the hourly rate of maintenance intravenous fluids. This method ensures that patients receive adequate hydration to match their metabolic needs based on body weight segments.

Formula: 4 mL/kg for the first 10kg, 2 mL/kg for the next 10kg, and 1 mL/kg for every kg thereafter.

Using the 4-2-1 Rule: an example

To illustrate this, consider a patient who weighs 25kg. Their weight is broken down into three components: 10kg, another 10kg, and the final 5kg.

Step-by-step calculation:

1. 10kg × 4 = 40 mL
2. 10kg × 2 = 20 mL
3. 5kg × 1 = 5 mL
4. Total = 65 mL/hr

Frequently Asked Questions

• Is this for neonates? No, neonates require different calculations based on day of life and specific glucose requirements.
• Does this include deficit replacement? No, this calculation is for maintenance fluid only. Fluid deficits from dehydration or ongoing losses must be added separately.
• When is this rule used? This rule is used for stable patients requiring intravenous hydration due to being nil per os (NPO) or unable to maintain oral intake.