Maintenance Fluids Calculator (4-2-1 Rule)
Holliday–Segar hourly and daily maintenance fluids — paediatrics' most-used formula.
Holliday and Segar derived this from caloric expenditure in 1957 and it still anchors paediatric prescriptions. Modern practice layers caution on top: maintenance is *not* resuscitation (deficits are replaced separately and faster), isotonic fluids are now preferred over the old hypotonic habit (hyponatraemia risk), and sick children often need less than calculated (ADH excess). The formula starts the prescription; the patient finishes it.
Formula
Reference aid for healthcare professionals only. Every result must be independently verified before clinical use. Never use this tool for self-medication or to replace clinical judgement.
Holliday–Segar hourly and daily maintenance fluids — paediatrics' most-used formula. The Maintenance Fluids Calculator (4-2-1 Rule) is a free, private 4-2-1 rule tool — every result computes instantly in your browser with no sign-up and no data upload.
About Maintenance Fluids Calculator (4-2-1 Rule)
Holliday and Segar derived this from caloric expenditure in 1957 and it still anchors paediatric prescriptions. It applies 4 mL/kg first 10 kg + 2 mL/kg next 10 + 1 mL/kg thereafter (per hour). Use the Maintenance Fluids Calculator (4-2-1 Rule) to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Maintenance Fluids Calculator (4-2-1 Rule)
- 1Enter your details in the Maintenance Fluids Calculator (4-2-1 Rule) input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Maintenance Fluids Calculator (4-2-1 Rule)?
- ✓Instant 4-2-1 rule result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Holliday MA & Segar WE, Pediatrics 1957)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Maintenance Fluids Calculator (4-2-1 Rule) work?+
Holliday and Segar derived this from caloric expenditure in 1957 and it still anchors paediatric prescriptions. The calculation uses the formula: 4 mL/kg first 10 kg + 2 mL/kg next 10 + 1 mL/kg thereafter (per hour). Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Maintenance Fluids Calculator (4-2-1 Rule) accurate, and what is it based on?+
The method is traceable to authoritative sources, including Holliday MA & Segar WE, Pediatrics 1957; NICE NG29 — IV fluids in children. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Maintenance Fluids Calculator (4-2-1 Rule) free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This is a reference aid for healthcare professionals and must be independently verified. It is not for self-diagnosis or self-medication.
What can I use the Maintenance Fluids Calculator (4-2-1 Rule) for?+
It's commonly used for 4-2-1 rule, maintenance fluids, holliday segar. Holliday–Segar hourly and daily maintenance fluids — paediatrics' most-used formula.
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