Calculators · Anaesthesiology · Formula
Holliday–Segar maintenance fluids (4-2-1 rule)
Also called 4-2-1 rule, 100-50-20 rule, maintenance IV fluid rate, paediatric maintenance fluids
Daily and hourly maintenance water requirement from body weight (100/50/20 mL/kg/day).
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Formula and scoring
100 mL/kg/day for the first 10 kg + 50 mL/kg/day for the next 10 kg + 20 mL/kg/day for each kg above 20. Hourly 4-2-1 (4 mL/kg/h, 2 mL/kg/h, 1 mL/kg/h) is the same rule divided by about 24.
Exam and ward pearls
- A 25 kg child: 1000 + 500 + 100 = 1600 mL/day (≈ 65 mL/h by 4-2-1).
When not to rely on it
- Applies to children beyond the neonatal period. Current guidance recommends isotonic maintenance fluid; some units use two-thirds of these rates.
Source
- Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823-32. doi:10.1542/peds.19.5.823 · PMID 13431307
- Hayes W, Sutcliffe AG, Peters MJ, et al. Intravenous fluid prescribing and complications in children in the UK and Ireland. Acta Paediatr. 2022;111(7):1450-1 (states the 100/50/20 mL/kg/day Holliday–Segar rates). doi:10.1111/apa.16295 · PMID 35170788
Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.