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Maintenance Fluid Calculator

Estimate pediatric maintenance fluids with the 4-2-1 rule from body weight. Use clinical judgment for real care decisions.

Maintenance fluid (Holliday-Segar)

Pounds are converted to kilograms before applying the rule.

Hourly maintenance rate (4-2-1 rule)

109.9 mL/hr

24-hour volume (100-50-20 rule): 2,497 mL/day (2.5 L/day)

Weight used
69.9 kg
24 h from 4-2-1 (rate x 24)
2,637 mL/day
First 10 kg (4 mL/kg/hr)
40 mL/hr
Next 10 kg (2 mL/kg/hr)
20 mL/hr
Above 20 kg (1 mL/kg/hr)
49.9 mL/hr

The 24-hour volume exceeds the common adult maintenance cap of 2,400mL/day. Many protocols cap maintenance near this point for adults. Confirm the target with your institution's policy.

For education only

The Holliday-Segar method estimates baseline maintenance fluid for a euvolemic patient. It does not account for existing deficits, ongoing losses (fever, vomiting, diarrhea, drains, burns), or conditions that limit fluid tolerance such as heart failure or kidney disease. This calculator is a study and double-check aid, not a substitute for professional medical advice or your facility's protocols. Always confirm any fluid order with the prescribing clinician.

Frequently Asked Questions about the Maintenance Fluid Calculator

What is the 4-2-1 rule for maintenance fluids?
The 4-2-1 rule gives an hourly maintenance fluid rate based on body weight. You give 4 mL/kg/hr for the first 10 kg, 2 mL/kg/hr for the next 10 kg (the 11th through 20th kg), and 1 mL/kg/hr for every kilogram above 20. For example, a 70 kg adult needs 40 plus 20 plus 50, which is 110 mL/hr.
How does the 4-2-1 rule relate to the 100-50-20 rule?
They are two forms of the same Holliday-Segar method. The 100-50-20 rule is the original 1957 daily version (100 mL/kg/day for the first 10 kg, 50 for the next 10 kg, and 20 per kg above 20), while 4-2-1 is the bedside hourly shortcut. They are close but not identical, because 4 mL/kg/hr times 24 hours is 96 mL/kg/day, not 100. This calculator shows the hourly rate, the 24-hour volume from 100-50-20, and the 24-hour total implied by 4-2-1 so you can compare them.
Should I use actual or ideal body weight?
The Holliday-Segar method was developed using actual body weight, so enter the patient's measured weight. In patients with obesity the rule can overestimate needs, and many clinicians switch to an adjusted or ideal body weight and a daily cap. Use clinical judgment and your local protocol for those cases.
Why is adult maintenance often capped around 2400 mL per day?
The 100-50-20 rule keeps adding 20 mL/kg/day for every kilogram, so it can produce very large volumes for heavy adults. Many protocols cap routine maintenance near 2400 mL/day, which the rule reaches at about 65 kg, to avoid fluid overload. This tool flags when your result passes that point instead of capping it for you, so you can apply your own policy.
Does this account for dehydration, fever, or fluid losses?
No. Maintenance fluids only replace normal ongoing losses in a euvolemic patient. You still need to add any existing deficit and ongoing losses from fever, vomiting, diarrhea, drains, or burns, and to reduce fluids in heart failure, kidney disease, or SIADH. Use a deficit and replacement calculation on top of the maintenance number.
Is this calculator a substitute for medical advice?
No. This tool is for education and quick double-checking only. It is not a substitute for professional medical advice, a prescriber's order, or your facility's protocols. Always confirm any IV fluid rate or volume with the responsible clinician before acting on it.

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