Enter Adult Fluid Details
Formula Used
Adult mL/kg/day method: Daily maintenance = calculation weight × selected mL/kg/day.
Holliday-Segar method: 100 mL/kg/day for the first 10 kg, 50 mL/kg/day for the next 10 kg, then 20 mL/kg/day above 20 kg.
4-2-1 method: 4 mL/kg/hour for the first 10 kg, 2 mL/kg/hour for the next 10 kg, then 1 mL/kg/hour above 20 kg.
Adjusted daily volume: Maintenance × target percent + ongoing losses - oral or enteral intake.
Total initial hourly rate: Adjusted daily volume ÷ 24 + deficit ÷ replacement hours.
Adjusted body weight: Ideal body weight + 0.4 × (actual weight - ideal body weight).
How to Use This Calculator
- Enter adult weight and select kg or lb.
- Enter height and sex if ideal or adjusted weight is needed.
- Select actual, ideal, or adjusted body weight.
- Choose the maintenance fluid method.
- Add losses, intake, deficit, and replacement hours.
- Use the daily cap only when clinically appropriate.
- Press the calculate button to view the result above the form.
- Download CSV or PDF if a record is needed.
Example Data Table
| Case | Weight | Method | Maintenance | Hourly Rate | Note |
|---|---|---|---|---|---|
| Standard adult | 70 kg | 30 mL/kg/day | 2100 mL/day | 87.5 mL/hour | Before losses or deficit |
| Lower target | 70 kg | 25 mL/kg/day | 1750 mL/day | 72.92 mL/hour | Review frailty risks |
| Holliday-Segar | 70 kg | 100/50/20 | 2500 mL/day | 104.17 mL/hour | Stepped weight formula |
| 4-2-1 rule | 70 kg | 4-2-1 | 2640 mL/day | 110 mL/hour | Hourly shortcut |
Adult Maintenance Fluid Planning
Adult maintenance fluid calculation estimates the water needed when a patient cannot meet normal intake. It is not a replacement for assessment. It supports a first pass review of daily volume, hourly rate, and extra fluid needs. The result should always be checked against observations, urine output, blood results, medicines, and the treatment plan.
Why Weight Matters
Most maintenance estimates start with body weight. This page lets you use actual, ideal, or adjusted weight. That helps when actual weight may not reflect active fluid need. It also helps avoid very large rates in some patients. The calculator can apply a daily cap, then show the effect on the hourly pump rate.
Choosing a Method
The adult guideline option uses a selected millilitre per kilogram per day target. Common choices include 25, 30, or 35 mL/kg/day. A custom value is also available. The Holliday-Segar option uses stepped weight bands. The 4-2-1 option gives the same style of result as an hourly shortcut. These methods are estimates, not final orders.
Losses, Deficit, and Intake
Maintenance alone may be too low if the patient has fever, drains, vomiting, diarrhoea, or high urine output. Enter ongoing losses as a daily amount. Enter oral or enteral intake if part of the need is already covered. A fluid deficit can also be entered with a replacement period. The tool then separates baseline rate from deficit rate.
Review Before Use
Fluid plans can harm patients when risk factors are ignored. Older, frail, cardiac, renal, hepatic, postoperative, septic, or malnourished patients may need a lower target or closer monitoring. Electrolyte needs also vary. Use the sodium, potassium, chloride, and glucose estimates as prompts for review. Confirm local policy and clinician instructions before acting.
Practical Output
The result section shows daily maintenance, adjusted daily volume, hourly rate, deficit rate, total pump rate, bags per day, and bag duration. You can export the calculation as CSV or PDF for notes, handover, audit, or teaching. Keep patient identifiers out of downloaded files unless your setting permits it. Printed figures should be dated. Recheck values when weight, intake, losses, or laboratory results change. Clear documentation improves safety and reduces calculation mistakes during busy handovers and reviews.
FAQs
What does this calculator estimate?
It estimates adult maintenance fluid needs from weight and selected method. It also adjusts for losses, intake, deficit replacement, and bag timing.
Can this result be used as a prescription?
No. It is an educational estimate. A clinician must review diagnosis, blood results, renal function, cardiac status, fluid balance, and local policy.
Which formula should I choose?
Use the method preferred by your setting. Adult mL/kg/day is common for routine planning. Holliday-Segar and 4-2-1 are stepped weight approaches.
Why include ideal and adjusted weight?
Actual weight can overestimate needs in some patients. Ideal and adjusted weight options help compare estimates, especially when body size affects dosing judgment.
What does the daily cap do?
The cap limits calculated maintenance before losses are added. It is optional and should only be used when it matches clinical judgment or local guidance.
Are electrolyte numbers final orders?
No. Sodium, potassium, chloride, and glucose values are review prompts. Electrolyte prescribing depends on labs, medicines, organ function, and clinical risk.
Can I add vomiting or drain losses?
Yes. Enter estimated ongoing losses in mL per day. The calculator adds that amount to the maintenance requirement before showing the hourly rate.
What do CSV and PDF downloads include?
They include the main result values, formula method, weight basis, deficit rate, bag timing, and review prompts from the submitted calculation.