Example 1 — 8 kg child
An 8 kg child is entirely within the first 10 kg weight band.
- Hourly: 8 kg × 4 mL/kg/hr = 32 mL/hr.
- Daily: 8 kg × 100 mL/kg/day = 800 mL/day.
Answer: 32 mL/hr using 4-2-1; 800 mL/day using 100-50-20.
Pediatric Maintenance Fluids Calculator
Paediatric fluid calculation
What is this child’s maintenance fluid estimate?
For children aged 28 days to 18 years, enter the authorised calculation weight and verify the kilogram value before calculating the full-maintenance 4-2-1 hourly estimate and separate Holliday-Segar 100-50-20 daily estimate.
Age check
This calculator is scoped to ages 28 days to 18 years. Neonates and adults need age-appropriate fluid guidance.
Weight unit
Choose the documented unit. Kilograms are the authoritative calculation weight; g and lb are converted to kg and must be verified before calculation.
kg
Enter the calculation weight authorised by the applicable guideline or clinical plan, in kilograms.
Maintenance estimate only
This calculator is for children aged 28 days to 18 years. It estimates maintenance fluid requirements only and does not calculate dehydration deficit, ongoing losses, resuscitation fluid or other clinical fluid needs. The verified kilogram value is a calculation input, not a decision about whether actual, ideal, dry or another authorised weight basis is clinically appropriate.
Simple answer
How are paediatric maintenance fluids calculated?
For children aged 28 days to 18 years, use weight in kilograms and apply the common stepped 4-2-1 hourly convention or the 100-50-20 Holliday-Segar daily method. They use the same weight bands but are calculated separately.
Example: For a 15 kg child: first 10 kg gives 40 mL/hr and the next 5 kg gives 10 mL/hr, for a total of 50 mL/hr.
This is a maintenance estimate only. It does not calculate deficit replacement, ongoing losses or resuscitation fluid.
Clinical use and safety
When to use this calculator — and its limits
The arithmetic can be correct while the clinical decision is still wrong. These boundaries show what the calculator can and cannot establish.
When to use
- Use to calculate the common full-maintenance water estimate from body weight in children aged 28 days to 18 years when the applicable clinical guidance uses Holliday-Segar / 100-50-20 or the common 4-2-1 hourly convention.
- Use as a transparent arithmetic starting point, then apply the child-specific fluid plan prescribed by the treating team or protocol.
- Use the most appropriate current weight specified by the clinical guideline; some guidance recommends considering ideal body weight in larger children.
Key limitations
- The result is a full-maintenance estimate, not an automatic IV-fluid prescription. It does not include resuscitation, dehydration deficit, ongoing abnormal losses or replacement requirements.
- Many unwell children retain water and may require less than full maintenance. RCH guidance notes that the majority of unwell children may require about two-thirds maintenance unless dehydrated.
- The calculator is restricted to ages 28 days to 18 years. Neonates need age-specific guidance and patients older than 18 years need adult fluid guidance.
- Specialised conditions such as major electrolyte disturbance, cardiac, renal or liver impairment, trauma/burns, DKA, oncology hyperhydration and critical illness may require different fluid strategies.
- The formula estimates water volume only. It does not determine fluid composition, sodium, glucose, potassium, tonicity or monitoring frequency.
- In larger children and adolescents, guideline maxima differ. RCH Melbourne and Children’s Health Queensland use a normal maximum of 2,400 mL/day / 100 mL/hr, while other guidance may use different adult-sized limits; MedMaths leaves the formula uncapped and does not choose a universal maximum.
What MedMaths does not decide
- Whether IV fluids are required or whether enteral fluids are preferable.
- Whether to prescribe full maintenance, a restricted percentage, deficit replacement, resuscitation fluid or replacement of ongoing losses.
- Which IV solution, electrolyte additives, glucose content or monitoring plan is clinically appropriate.
- Whether the authorised calculation weight should be actual, ideal, dry or another clinically specified weight basis.
Evidence and method checks
- The maintenance need for water in parenteral fluid therapy — Holliday & Segar / Pediatrics / PubMed
- Clinical Practice Guideline: Intravenous fluids — Royal Children's Hospital Melbourne
- Intravenous fluid therapy in children and young people in hospital — NG29 — NICE
- Clinical Practice Guideline: Maintenance Intravenous Fluids in Children — American Academy of Pediatrics
- Pediatric Readiness in the Emergency Department: Technical Report — American Academy of Pediatrics
- ESPNIC clinical practice guidelines: intravenous maintenance fluid therapy in acute and critically ill children — ESPNIC / Intensive Care Medicine
Formula logic and known-value examples are checked as part of the MedMaths review process.
See how MedMaths checks calculator methods →What does the hourly result mean?
The mL/hr result is the calculator's hourly maintenance estimate from the entered weight using the 4-2-1 calculation.
What does the daily result mean?
The mL/day result is the daily Holliday-Segar maintenance estimate using the 100-50-20 calculation. It is not simply the displayed hourly rate multiplied by 24.
Maintenance is only one part of paediatric fluid assessment
This calculator does not account for dehydration deficit, ongoing losses, fever, postoperative or critical illness, or other patient-specific fluid needs. Follow the applicable paediatric fluid guideline and specialist advice.
This calculator determines volume, not the IV-fluid prescription
The AAP gives a strong Grade A recommendation for isotonic maintenance IV fluids with appropriate potassium chloride and dextrose for patients aged 28 days to 18 years within its studied scope because this reduces hospital-acquired hyponatraemia. Important exclusions include neurosurgical, cardiac, hepatic, renal and oncologic disease, diabetes insipidus, voluminous watery diarrhoea and severe burns. MedMaths calculates volume only; it does not select the fluid prescription.
Monitor the child and count total fluid exposure
Maintenance fluid is only one source of intake. Current guidance supports reassessing weight, fluid input/output and balance, electrolytes, glucose and the ongoing need for IV therapy. In acutely or critically ill children, ESPNIC also recommends counting IV medicines, bolus-drug volumes, line flushes, blood products and enteral intake when considering total daily maintenance-fluid exposure to reduce fluid creep.
Formula, examples and practical checks
Review the two formula conventions, representative examples, common calculation mistakes and focused calculator FAQs.
Formula, examples and practical checks
Review the two formula conventions, representative examples, common calculation mistakes and focused calculator FAQs.
How paediatric maintenance-fluid calculations work
- Enter the authorised calculation weight and select the documented unit.
- Verify the displayed kilogram calculation weight against the patient record before calculating. MedMaths never treats the selected weight basis as a clinical decision.
- Apply the first 10 kg at the first-band rate.
- Apply only the next 10 kg at the second-band rate.
- Apply only kilograms above 20 kg at the third-band rate.
- Add the bands together to produce the hourly 4-2-1 result and the separate daily 100-50-20 result.
The key idea: the bands are cumulative
A 25 kg child is not calculated as 25 × 1 mL/kg/hr. The first 10 kg still uses ×4, the next 10 kg uses ×2, and only the final 5 kg uses ×1.
The maintenance-fluid formulas
4-2-1 rule — hourly
In simple words
Work through the same three weight bands and add the hourly amounts together.
- First 10 kg
- = 4 mL/kg/hr
- Next 10 kg
- = 2 mL/kg/hr
- >20 kg
- = 1 mL/kg/hr for each kilogram above 20
100-50-20 rule — daily
In simple words
This is the stepped daily maintenance-water method described from the Holliday-Segar approach.
- First 10 kg
- = 100 mL/kg/day
- Next 10 kg
- = 50 mL/kg/day
- >20 kg
- = 20 mL/kg/day for each kilogram above 20
Method relationship
100-50-20 is the daily Holliday-Segar method; 4-2-1 is a later rounded hourly shortcut based on the same bands.
Why 4-2-1 and 100-50-20 can differ →| Weight band | Hourly 4-2-1 | Daily 100-50-20 |
|---|---|---|
| First 10 kg | 4 mL/kg/hr | 100 mL/kg/day |
| Next 10 kg | 2 mL/kg/hr | 50 mL/kg/day |
| Each kg above 20 kg | 1 mL/kg/hr | 20 mL/kg/day |
Worked examples
These examples teach the weight-band arithmetic only. They do not prescribe a fluid type or determine whether full maintenance is clinically appropriate.
Example 2 — 55.1 lb child (about 25 kg)
Convert pounds to kilograms first, then apply the stepped weight bands. MedMaths does this conversion automatically when lb is selected.
- 55.1 lb × 0.45359237 ≈ 25.0 kg.
- Hourly: 40 + 20 + 5 ≈ 65 mL/hr.
- Daily: 1,000 + 500 + 100 ≈ 1,600 mL/day.
Answer: About 65 mL/hr using 4-2-1; about 1,600 mL/day using 100-50-20.
Common paediatric maintenance-fluid mistakes
Applying one multiplier to the whole weight
The calculation is stepped. A 25 kg child is not 25 × 1 mL/kg/hr; the first 20 kg still uses the earlier bands.
Treating hourly × 24 as the daily rule
4-2-1 uses rounded hourly coefficients, so multiplying the displayed hourly rate by 24 may not equal the separate 100-50-20 daily result.
Calling maintenance the total fluid requirement
Maintenance does not automatically include dehydration deficit, resuscitation volume or ongoing abnormal losses.
Using full maintenance automatically
The formula is a starting estimate. Unwell children may need a restricted or otherwise adjusted rate according to the applicable guideline.
Using the calculator outside the paediatric age scope
Patients under 28 days need neonatal guidance and patients older than 18 years need adult fluid guidance; both are blocked by the calculator age check.
Using the wrong weight unit
kg, g and lb are supported for entry, but kilograms are the authoritative calculation weight. Verify the displayed kg value before calculating.
Ignoring other sources of intake
Maintenance IV fluid, IV medicines, bolus-drug volumes, line flushes, blood products and enteral intake can all contribute to total fluid exposure.
Frequently Asked Questions
Need the explanation or more practice?
Understand why 4-2-1 and 100-50-20 differ, plus the clinical limits →Practise paediatric maintenance-fluid calculations in Learn →Continue calculating
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Calculate mg/kg per-dose or per-day orders using kg or lb, divided doses, and liquid concentration.
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Calculate adult Devine ideal body weight in cm or feet and inches, with optional Robinson and Miller comparison estimates.
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Calculate drops per minute from mL/hr or from total volume and infusion time.
Open calculatorReferences and sources
Open the original Holliday-Segar paper and current paediatric and neonatal fluid guidance used for this evidence review.
References and sources
Open the original Holliday-Segar paper and current paediatric and neonatal fluid guidance used for this evidence review.
Original Holliday-Segar publication
Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823–832. DOI: 10.1542/peds.19.5.823.
NICE — routine maintenance and neonatal age-specific guidance
NICE Guideline NG29: Intravenous fluid therapy in children and young people in hospital. Includes Holliday-Segar 100-50-20 maintenance calculation, usual adult-sized maximums and separate neonatal daily volumes.
NICE NG29 recommendationsRoyal Children's Hospital Melbourne — IV fluids
RCH Clinical Practice Guideline: Intravenous fluids. Applies to children aged 1 month to 18 years, separates maintenance from deficits and ongoing losses, and lists a normal maximum of 2,400 mL/day / 100 mL/hr above 60 kg.
RCH intravenous fluids guidelineRoyal Children's Hospital Melbourne — neonatal IV fluids
Separate neonatal guidance uses day-of-life and gestation-specific fluid requirements, supporting the calculator's under-28-day guardrail.
RCH neonatal IV fluids guidelineAmerican Academy of Pediatrics — maintenance IV fluid tonicity
Feld LG, et al. Clinical Practice Guideline: Maintenance Intravenous Fluids in Children. Pediatrics. 2018;142(6):e20183083. The guideline recommends isotonic solutions with appropriate potassium chloride and dextrose for patients aged 28 days to 18 years within its scope, and lists important excluded high-risk groups requiring separate clinical guidance.
American Academy of Pediatrics — kilogram-only paediatric weight safety
The 2026 AAP Pediatric Readiness technical report recommends weighing all children in kilograms and recording the kg weight prominently. MedMaths therefore treats kilograms as the authoritative calculation weight even when g or lb are entered for convenience.
AAP Pediatric Readiness technical reportESPNIC — total fluid exposure and reassessment
Brossier DW, et al. ESPNIC clinical practice guidelines: intravenous maintenance fluid therapy in acute and critically ill children. Intensive Care Med. 2022;48:1691–1708. The guideline recommends considering all maintenance-fluid sources, including IV medicines, flushes, blood products and enteral intake, and reassessing fluid balance and electrolytes.
Open-access ESPNIC guidelineSystematic review — isotonic versus hypotonic maintenance fluid
An updated systematic review and meta-analysis included 33 randomised trials and 5,049 children and found isotonic maintenance fluids reduced mild hyponatraemia compared with hypotonic fluids, while also reinforcing the need for patient-specific monitoring.
PubMed PMID 37365423Children’s Health Queensland — paediatric maintenance fluids
Queensland Paediatric Emergency Care maintenance-fluid guidance uses the 4-2-1 calculation, a 100 mL/hr / 2,400 mL/day maximum and strict fluid-balance monitoring.
Queensland paediatric emergency skill sheets