Maintenance Fluids Calculator
What is Maintenance Fluids Calculator
The maintenance fluids calculator works out the baseline intravenous fluid a patient needs to stay in balance, using the Holliday-Segar weight-based method. It gives 100 mL/kg per day for the first 10 kg, 50 mL/kg for the next 10 kg and 20 mL/kg for each kilogram beyond 20, and it also shows the hourly rate from the matching 4-2-1 rule.
How to use
- Enter the body weight in kilograms.
- Read the total maintenance volume per day.
- Read the hourly infusion rate from the 4-2-1 rule.
- Add deficits and ongoing losses separately as clinically needed.
When to use it
A 20 kg child needs maintenance fluids and you want a quick starting rate? Enter 20 kg and you get 1500 mL per day and 60 mL per hour, ready to set the pump. It is the fast bedside step for prescribing maintenance, on top of which you add any fluid deficit and replace ongoing losses.
Frequently asked questions
What is the Holliday-Segar method?
It is the classic weight-based estimate of daily maintenance fluid: 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg, and 20 mL/kg for each kilogram over 20. The 4-2-1 rule is the hourly version of the same tiers.
Does this include deficits or ongoing losses?
No. It estimates baseline maintenance only. Any existing dehydration deficit and continuing losses such as vomiting, diarrhoea or drains must be added on top and replaced separately.
Is it valid for adults?
It is most accurate in children. In adults the Holliday-Segar volume can overestimate needs, so a lower or capped rate is often used, and it should always be checked against the clinical picture.
Can I share this tool with my inputs pre-filled?
Yes. The URL updates automatically as you type. Copy it from the address bar or use the Copy link button, and anyone who opens the link will see your exact inputs ready to go.
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