Maintenance Fluid Calculator

How it is calculated

The tool applies the Holliday-Segar tiers to body weight W in kilograms: Daily = 100 × min(W, 10) + 50 × (min(W, 20) − 10, not below 0) + 20 × (W − 20, not below 0), in millilitres per day. In words: 100 mL per kg for the first 10 kg, 50 mL per kg for the next 10 kg, and 20 mL per kg for each kg above 20. The hourly rate is simply the daily total divided by 24.

The result is the total for the whole body, not per kilogram. The weight must be above zero. The daily volume is rounded to a whole mL and the hourly rate to one decimal. This is a baseline maintenance estimate only: it does not include fluid deficits, ongoing losses or restrictions, which a clinician adds or adjusts separately, and it is not a prescription.

Common mistakes

• Entering weight in pounds. The field is in kilograms; convert first (divide pounds by about 2.2).
• Applying 100 mL/kg to the whole body weight. Only the first 10 kg get 100; the next 10 kg get 50, and the rest 20.
• Reading the result as per-kg. The 1600 mL/day is the total for the patient, not mL/kg.
• Treating maintenance as the full fluid order. Dehydration, ongoing losses, fever or fluid restriction are not included.
• Forgetting the rounding. The hourly rate is rounded to one decimal, so a pump setting may need to follow your local protocol.