This tool estimates maintenance fluid needs using standard weight-based rules, optional clinical modifiers, ongoing losses, and NPO deficit review. It supports education and planning, not independent prescribing.
Enter Patient Values
Example Data Table
| Case | Weight | Temperature | Losses | NPO | Estimated Hourly Rate |
|---|---|---|---|---|---|
| Child routine maintenance | 18 kg | 37.0°C | 0 mL/day | 0 hours | 56 mL/hr |
| Adult with fever | 70 kg | 38.0°C | 0 mL/day | 0 hours | 121 mL/hr |
| Pediatric with GI losses | 24 kg | 37.5°C | 240 mL/day | 4 hours | 74 mL/hr |
Formula Used
1) Holliday-Segar daily rule
Daily maintenance volume = 100 mL/kg for the first 10 kg, plus 50 mL/kg for the next 10 kg, plus 20 mL/kg for each kg above 20.
2) 4-2-1 hourly rule
Hourly maintenance rate = 4 mL/kg/hr for the first 10 kg, plus 2 mL/kg/hr for the next 10 kg, plus 1 mL/kg/hr for each kg above 20.
3) Fever adjustment
Adjusted maintenance = base maintenance × (1 + 10% for each full °C above 37).
4) Ongoing loss replacement
Total hourly rate = adjusted maintenance hourly rate + ongoing losses per hour. Ongoing losses per hour = daily measurable losses ÷ 24.
5) NPO deficit
NPO deficit = adjusted maintenance hourly rate × NPO hours. A common teaching approach replaces 50% in the first 8 hours, then 25% in the next 16 hours, and 25% later.
6) Optional adjusted body weight
Adjusted body weight = ideal body weight + 0.4 × (actual body weight − ideal body weight).
How to Use This Calculator
Enter body weight and choose kilograms or pounds.
Add age, sex, and height if you want optional adjusted weight support.
Select the preferred method for viewing the maintenance estimate.
Enter temperature to apply a simple fever-related adjustment.
Add measurable ongoing losses such as drain or GI output.
Enter NPO hours to estimate a maintenance-based fluid deficit.
Choose a rounding step for cleaner bedside pump settings.
Press the calculate button to show results above the form.
Use the CSV button to export structured values.
Use the PDF button to print or save the page as a PDF.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates maintenance IV fluid volume per day and hour using standard weight-based rules. It can also add simple modifiers, ongoing measurable losses, and NPO deficit review.
2) Which rule is used for the main calculation?
The calculator uses the Holliday-Segar daily rule and the 4-2-1 hourly rule. Both are shown so clinicians can review daily and hourly maintenance values together.
3) Why is fever included as an option?
Fever may increase insensible losses. This tool applies a simple educational adjustment of 10% per full degree Celsius above 37°C, but actual prescribing should follow clinical judgment.
4) Should ongoing losses be included in maintenance fluid?
Measurable losses are usually replaced separately from baseline maintenance. This calculator adds them to the displayed hourly and daily totals so the impact is easy to review.
5) What is the purpose of the NPO deficit section?
The NPO deficit estimates maintenance fluid missed during fasting. The phased replacement values are educational and may differ from local protocols or patient-specific needs.
6) When should adjusted body weight be considered?
Adjusted body weight may be considered in selected overweight adults for dose or volume estimation. It is not a universal replacement for actual weight in every fluid decision.
7) Can I use this for neonates or critically ill patients?
Use extra caution. Neonates, critical illness, renal dysfunction, cardiac disease, liver disease, burns, shock, and electrolyte disorders require protocol-based prescribing and close monitoring.
8) Does this tool choose the fluid type?
No. It estimates volume and rate only. Fluid composition, electrolytes, dextrose content, sodium strategy, and monitoring plan must be chosen by the treating clinician.