Maintenance Fluid Calculator

About this calculator

This calculator applies the Holliday-Segar "100/50/20" rule, the standard pediatric formula for daily maintenance IV fluid: 100 mL/kg for the first 10 kg of body weight, plus 50 mL/kg for the next 10 kg, plus 20 mL/kg for every kilogram above 20. Dividing the 24-hour total by 24 gives the hourly infusion rate, often shortened to the bedside "4-2-1 rule" (4 mL/kg/hr for the first 10 kg, 2 mL/kg/hr for the next 10, 1 mL/kg/hr thereafter) — the same formula expressed per hour instead of per day.

Pediatric nurses and physicians use this to set baseline IV fluid rates for children who can't take fluids by mouth, and it's a routine calculation taught in pediatric advanced life support and nursing programs. It gives maintenance needs only — it doesn't account for dehydration deficits, ongoing losses, or fluid restriction in conditions like heart or kidney disease, which a clinician adjusts for separately.