Maintenance Fluids Calculator (4-2-1)

About this calculator

This calculator finds the hourly maintenance IV fluid rate using the 4-2-1 rule (also called the Holliday-Segar method): 4 mL/kg/hr for the first 10 kg of body weight, 2 mL/kg/hr for the next 10 kg, and 1 mL/kg/hr for every kg above 20. It's the standard bedside method for estimating baseline fluid needs.

Nurses, physicians, and nursing or medical students use it to set a starting maintenance infusion rate for a patient who isn't taking in fluids normally. Enter the patient's weight to get the hourly rate in mL/hr.