Calcoid

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.

Maintenance Fluid Reference

The calculator reports both established conventions. Clinical fluid needs can differ from either estimate.

Weight4-2-1 hourly rate100-50-20 daily volumeHourly rate × 24
5 kg20 mL/hour500 mL/day480 mL/day
10 kg40 mL/hour1,000 mL/day960 mL/day
20 kg60 mL/hour1,500 mL/day1,440 mL/day
30 kg70 mL/hour1,750 mL/day1,680 mL/day
70 kg110 mL/hour2,500 mL/day2,640 mL/day

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 calculation. The 100-50-20 rule is the 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 an 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 both outputs. It does not determine whether either method is appropriate for an individual patient.
Should I use actual or ideal body weight?
The calculator applies the formula to the weight you enter. It cannot determine the clinically appropriate weight basis or fluid plan. In obesity, fluid overload risk, kidney disease, heart failure, or critical illness, the method and any cap must be selected by the treating team under the applicable protocol.
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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