Maintenance Fluids Calculator
Calculate maintenance IV fluid requirements using the Holliday-Segar 4-2-1 rule, for adults and children by weight. Educational tool only.
How the daily total is built
| Bracket | Weight | Volume |
|---|---|---|
| First 10 kg (100 mL/kg/day) | 10.0 kg | 1,000 mL |
| Next 10 kg (50 mL/kg/day) | 10.0 kg | 500 mL |
| Each kg above 20 (20 mL/kg/day) | 55.0 kg | 1,100 mL |
Holliday-Segar estimates maintenance fluid for a patient who cannot drink, based on weight. It does not account for ongoing losses from fever, vomiting, diarrhoea, burns, drains or high-output stomas, which have to be replaced separately, nor for fluid restriction in heart or kidney failure. In practice, maintenance fluid is often capped in adults and adjusted to the clinical picture.
Frequently asked questions
What is the 4-2-1 rule for fluids?
The 4-2-1 rule gives hourly maintenance fluids: 4 mL per kilogram per hour for the first 10 kg of body weight, 2 mL/kg/hr for the next 10 kg, and 1 mL/kg/hr for every kilogram thereafter.
What is the Holliday-Segar method?
Holliday-Segar calculates the same requirement over 24 hours: 100 mL per kilogram per day for the first 10 kg, 50 mL/kg/day for the next 10 kg, and 20 mL/kg/day beyond that.
Do maintenance fluids cover everyone?
No. Maintenance fluid estimates do not account for existing deficits, ongoing losses, cardiac or renal impairment, or post-operative requirements. Clinical judgement and local guidelines always take precedence.
Related calculators
eGFR Calculator
Estimate glomerular filtration rate (eGFR) with the CKD-EPI 2021 equation, with the CKD stage for the result. Educational tool only.
Creatinine Clearance Calculator
Calculate creatinine clearance (CrCl) with the Cockcroft-Gault equation โ widely used for renal drug dosing. Educational tool only.
Anion Gap Calculator
Calculate the anion gap and the albumin-corrected anion gap from sodium, chloride, bicarbonate and albumin. Educational tool only.
Infusion Rate Calculator
Work out infusion rate in mL/hour and drops per minute from volume and time โ the standard IV drip rate calculation. Educational tool only.