Maintenance Fluid Calculator

How the Maintenance Fluid Calculator Works

The Holliday-Segar method estimates a patient’s daily maintenance fluid needs from body weight. The hourly “4-2-1” rule gives 4 mL/kg/hour for the first 10 kg of weight, 2 mL/kg/hour for the next 10 kg, and 1 mL/kg/hour for every kilogram above 20. Enter the weight to get the hourly rate and the equivalent daily volume.

These are baseline maintenance needs for a well patient; they do not account for dehydration, ongoing losses, fever or other factors, which require additional replacement. It is most often used in paediatrics.

4 mL/kg (first 10 kg) + 2 mL/kg (next 10 kg) + 1 mL/kg (each kg > 20)