Maintenance Fluid Calculator

Category: Other Health
- December 10, 2025
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Calculate the maintenance fluid requirements based on body weight using the Holliday-Segar method. This calculator helps determine the appropriate IV fluid rate for patients.

Patient Information

Advanced Settings

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About Maintenance Fluid Calculations

Maintenance fluids are designed to replace normal daily water and electrolyte losses through urine, stool, sweat, and insensible losses (through respiration and skin).

Holliday-Segar Method (4-2-1 Rule)
  • First 10 kg: 4 mL/kg/hour
  • Second 10 kg: 2 mL/kg/hour
  • Each additional kg: 1 mL/kg/hour
Body Surface Area Method

1,500 mL/m² per 24 hours

Simplified Method
  • ≤ 10 kg: 100 mL/kg/day
  • 10-20 kg: 1000 mL + 50 mL/kg for each kg > 10
  • > 20 kg: 1500 mL + 20 mL/kg for each kg > 20

Disclaimer: This calculator provides estimates based on standard formulas and should be used only as a guide. Clinical judgment should always supersede calculator results. Fluid requirements may need adjustment based on the patient's clinical condition, ongoing losses, and other factors. This tool is not meant to replace medical advice or clinical assessment.

Holliday-Segar Method (4-2-1 Rule):
• First 10 kg: 4 mL/kg/hour
• Next 10 kg: 2 mL/kg/hour
• Each additional kg: 1 mL/kg/hour

Simplified Method:
• ≤ 10 kg: 100 mL/kg/day
• 10–20 kg: 1,000 mL + 50 mL/kg for weight above 10 kg
• > 20 kg: 1,500 mL + 20 mL/kg for weight above 20 kg

Body Surface Area (BSA) Method:
Daily Fluid = BSA (m²) × 1,500 mL

What Is the Maintenance Fluid Calculator?

The Maintenance Fluid Calculator is a practical tool designed to estimate daily and hourly fluid requirements for individuals based on their body weight, age group, and clinical considerations. It simplifies the process of fluid planning, especially in clinical settings where intravenous (IV) hydration is necessary.

This calculator uses proven formulas like the Holliday-Segar Method, the Simplified 100/50/20 Rule, and the Body Surface Area estimation to provide accurate fluid needs based on different scenarios and patient categories.

Why Use This Calculator?

Proper hydration is essential for patients, especially those who cannot intake fluids orally. This tool supports clinicians, nurses, and healthcare staff by providing:

  • Quick estimates of daily and hourly fluid needs
  • Multiple calculation methods for flexibility
  • Advanced settings for sodium and dextrose concentrations
  • Optional adjustments for elderly and obese patients
  • Detailed breakdowns to support educational or documentation needs

How to Use the Maintenance Fluid Calculator

Follow these steps to use the calculator effectively:

  • Step 1: Enter the patient's weight and choose between kilograms or pounds.
  • Step 2: Select the calculation method that fits your clinical context.
  • Step 3: Choose the patient’s age category — paediatric, adult, or elderly.
  • Step 4: (Optional) Check the box for adjusted weight if dealing with an obese patient.
  • Step 5: Adjust sodium and dextrose concentrations as needed for fluid type preference.
  • Step 6: Click "Calculate Maintenance Fluids" to view the results and detailed breakdown.

How It Helps

This tool can be a daily companion for medical professionals handling hydration therapy. It enhances clinical efficiency, reduces calculation errors, and ensures that fluid plans align with the patient’s specific needs. Whether managing a paediatric dehydration case or fine-tuning IV rates for elderly patients, this calculator provides data-driven guidance.

While not a diagnostic device, it serves a similar role to Other supportive tools like the GFR Calculator (for kidney function), the Corrected Calcium Calculator (for electrolyte adjustments), and the Body Surface Area Calculator (used in chemotherapy or dosing decisions).

Frequently Asked Questions (FAQ)

Q: What is the 4-2-1 rule?

A formula for calculating hourly maintenance fluid rates: 4 mL/kg for the first 10 kg, 2 mL/kg for the next 10 kg, and 1 mL/kg for each kg thereafter.

Q: Can this calculator be used for adults?

Yes. It includes categories for adult and elderly patients, with options for adjusted body weight in obesity.

Q: Does it replace clinical judgment?

No. This tool is a guideline. Always consider clinical signs, lab values, and physician recommendations when planning fluid therapy.

Q: Is the Body Surface Area (BSA) method accurate without height?

This calculator uses a simplified estimation based on weight alone, which is generally acceptable for quick assessments.

Q: Can this calculator be used alongside other tools?

Yes. It's similar to using a Paracetamol Dosage Calculator for pain management or a Sobriety Calculator to track sobriety milestones. It complements clinical care planning.

Final Note

The Maintenance Fluid Calculator simplifies fluid planning using medically accepted methods. It’s a reliable tool to support hydration strategies and can help prevent both underhydration and fluid overload. Remember, it should be used with clinical awareness and not as a substitute for direct medical advice.