Maintenance Fluids Calculator

Estimate maintenance IV fluid volume and rate from body weight using the Holliday-Segar method (the 4-2-1 rule), with an optional adjustment for fever and ongoing losses.

Quick Facts

Formula
Holliday-Segar method (4-2-1 rule)
4 mL/kg/hr for the first 10 kg, 2 mL/kg/hr for the next 10 kg, 1 mL/kg/hr for each kg above 20.
Fever adjustment
About 12% per deg C above 37.8 deg C
A clinical rule-of-thumb reflecting increased insensible losses during fever.

Your Results

Calculated
Base daily maintenance
-
Holliday-Segar volume, mL/day
Base hourly rate
-
4-2-1 rule, mL/hr
Fever + extra losses
-
Added volume, mL/day
Total adjusted fluids
-
Daily total and rate

Ready

Enter body weight to calculate maintenance IV fluid needs using the Holliday-Segar method.

About the Maintenance Fluids Calculator

This calculator estimates maintenance intravenous fluid needs from body weight using the Holliday-Segar method, published in 1957 and still the standard weight-based formula for maintenance fluids in children and adults who cannot meet fluid needs by mouth. It reports both a daily volume and an hourly infusion rate, with an optional adjustment for fever and any ongoing losses you enter.

How the calculation works

  • For body weight up to 10 kg, maintenance fluid is 100 mL/kg/day, equivalent to 4 mL/kg/hr.
  • For the portion of weight from 10 to 20 kg, add 50 mL/kg/day (2 mL/kg/hr) on top of the first band.
  • For any weight above 20 kg, add 20 mL/kg/day (1 mL/kg/hr) on top of the first two bands.

Putting the result in context

The base result is a starting maintenance volume, not a complete fluid order. Fever raises insensible losses through the skin and lungs, so this tool adds roughly 12% to the base volume for each degree Celsius above 37.8 deg C (100.4 deg F) - a commonly used clinical estimate rather than a measured value. Any ongoing losses you enter, such as vomiting, diarrhea, or drain output, are added on top as a separate line so the base calculation and the adjustments stay visible.

When to consult a professional

This tool performs the standard Holliday-Segar arithmetic for education and planning. It does not select fluid type, dextrose or electrolyte content, correct a pre-existing deficit, or account for renal, cardiac, or hepatic disease. Any actual fluid order should be confirmed by the treating clinician based on the full clinical picture.

Frequently Asked Questions

What formula does this maintenance fluids calculator use?
It uses the Holliday-Segar method, the standard weight-based formula for maintenance IV fluids. Daily volume is 100 mL/kg for the first 10 kg of body weight, plus 50 mL/kg for each kilogram from 10 to 20 kg, plus 20 mL/kg for each kilogram above 20 kg. The same bands give an hourly rate of 4, 2, and 1 mL/kg/hr respectively — often called the 4-2-1 rule.
How does fever change maintenance fluid needs?
Fever increases insensible water loss through the skin and lungs. A commonly used clinical rule adds roughly 10 to 15 percent to the maintenance volume for each degree Celsius above 37.8 degrees C (100.4 degrees F); this calculator uses 12 percent per degree as a mid-range estimate. It is a general adjustment, not a measured value for any individual patient.
Does this replace a clinician's fluid order?
No. This tool estimates a starting maintenance volume and rate from weight alone. It does not select fluid type, dextrose or electrolyte content, correct pre-existing deficits, or account for renal, cardiac, or hepatic disease. Fluid orders should always be confirmed by the treating clinician.

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