Fluids & Medications

Maintenance Fluid Calculator

Calculates daily and hourly maintenance fluid requirements using the Holliday-Segar method.

When to use: Used to calculate baseline fluid requirements in patients who cannot maintain adequate oral intake — primarily paediatric patients, but also adults post-operatively. Remember this formula estimates insensible losses and does not account for third-spacing or ongoing losses.

Calculator

Weight(kg)

Fill in all fields to see the result

Formula

First 10 kg: 100 mL/kg/day Next 10 kg (10–20 kg): 50 mL/kg/day >20 kg: 20 mL/kg/day "4-2-1" rule for hourly rate: 4 mL/kg/hr for first 10 kg + 2 mL/kg/hr for next 10 kg + 1 mL/kg/hr for each kg >20

Key Points for NEET PG

Holliday-Segar (1957) — the "4-2-1" rule for hourly rates is the clinical shorthand
Standard maintenance fluid in children: 0.45% NaCl + 5% dextrose + 20 mEq/L KCl
Isotonic fluids (0.9% NaCl) preferred in post-op or sick children — risk of hyponatraemia with hypotonic fluids
Formula underestimates requirements in burns, fever (add 12% per °C above 38), or excessive losses
Mnemonic: "100-50-20 rule" for mL/kg/day; "4-2-1 rule" for mL/kg/hr

References

The maintenance need for water in parenteral fluid therapy · Pediatrics (1957)

For educational purposes only. Not for clinical decision-making without professional oversight.