{
  "id": "maintenance-fluid",
  "version": "2c07e2843743",
  "status": "published",
  "name": "Maintenance Fluid Calculator",
  "question": "What is the maintenance fluid rate?",
  "summary": "Calculates the maintenance fluid volume per day by the Holliday-Segar method and the hourly rate by the 4-2-1 rule from body weight.",
  "category": "health",
  "subcategory": "clinical",
  "url": "https://www.acalculator.org/health/maintenance-fluid-calculator",
  "markdown": "https://www.acalculator.org/health/maintenance-fluid-calculator.md",
  "kind": "function",
  "method": "Per day: 100 mL/kg for the first 10 kg + 50 mL/kg for 10 to 20 kg + 20 mL/kg above 20 kg. Per hour (4-2-1): 4 mL/kg + 2 mL/kg + 1 mL/kg over the same bands.",
  "assumptions": [
    "The Holliday-Segar method estimates water needs from calories burned; it gives a volume, not a fluid type.",
    "Newborns in the first weeks of life and people with kidney, heart, or hormone disorders need other rules.",
    "The daily volume is rounded to a whole mL and each hourly rate to 1 decimal, halves up."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "weight": {
        "title": "Weight",
        "description": "Body weight, 3 kg (6.6 lb) or more.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "mass",
        "minimum": 3,
        "maximum": 150
      }
    }
  },
  "outputs": {
    "daily": {
      "label": "Per day (Holliday-Segar)",
      "description": "Maintenance fluid in mL per day: 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10, 20 mL/kg above 20 kg.",
      "format": "number"
    },
    "hourly": {
      "label": "Per hour (daily ÷ 24)",
      "description": "The daily volume spread over 24 hours, in mL per hour, to 1 decimal.",
      "format": "number"
    },
    "rule421": {
      "label": "Per hour (4-2-1 rule)",
      "description": "The 4-2-1 rule: 4 mL/kg/h for the first 10 kg, 2 for the next 10, 1 above 20 kg, to 1 decimal.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "weight": 15
    },
    "outputs": {
      "daily": 1250,
      "hourly": 52.1,
      "rule421": 50
    },
    "text": "The maintenance fluid is 1,250 mL per day, or 50 mL per hour by the 4-2-1 rule."
  },
  "examples": [
    {
      "given": {
        "weight": 8
      },
      "expect": {
        "daily": 800,
        "hourly": 33.3,
        "rule421": 32
      },
      "source": "Holliday and Segar 1957: 100 × 8 = 800 mL/day; 800 ÷ 24 = 33.33; 4 × 8 = 32 mL/h (hand calculation in content.mdx)"
    },
    {
      "given": {
        "weight": 15
      },
      "expect": {
        "daily": 1250,
        "hourly": 52.1,
        "rule421": 50
      },
      "source": "1,000 + 50 × 5 = 1,250 mL/day; ÷ 24 = 52.08; 40 + 2 × 5 = 50 mL/h (hand calculation in content.mdx)"
    },
    {
      "given": {
        "weight": 30
      },
      "expect": {
        "daily": 1700,
        "hourly": 70.8,
        "rule421": 70
      },
      "source": "1,500 + 20 × 10 = 1,700 mL/day; ÷ 24 = 70.83; 60 + 10 = 70 mL/h (hand calculation in content.mdx)"
    },
    {
      "given": {
        "weight": 70
      },
      "expect": {
        "daily": 2500,
        "hourly": 104.2,
        "rule421": 110
      },
      "source": "1,500 + 20 × 50 = 2,500 mL/day; ÷ 24 = 104.17; 60 + 50 = 110 mL/h (hand calculation in content.mdx)"
    },
    {
      "given": {
        "weight": 9.071847400000001
      },
      "expect": {
        "daily": 907,
        "hourly": 37.8,
        "rule421": 36.3
      },
      "source": "100 × 9.0718 = 907.18 mL/day; ÷ 24 = 37.80; 4 × 9.0718 = 36.29 mL/h (hand calculation in content.mdx)"
    }
  ],
  "sources": [
    "Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823-832. https://doi.org/10.1542/peds.19.5.823",
    "Feld LG, Neuspiel DR, Foster BA, et al. Clinical practice guideline: maintenance intravenous fluids in children. Pediatrics. 2018;142(6):e20183083. https://doi.org/10.1542/peds.2018-3083",
    "National Institute of Standards and Technology. NIST Special Publication 811, Appendix B (1 lb = 0.45359237 kg). https://www.nist.gov/pml/special-publication-811"
  ],
  "related": [],
  "changelog": [
    {
      "date": "2026-09-30",
      "note": "Published after this site's editorial review against the cited sources (no clinician review); the page notices say so."
    }
  ]
}