How do you calculate maintenance IV fluids (4-2-1 rule)?

**Holliday-Segar (4-2-1)** gives **hourly mL/hr**: **4 mL/kg/hr** for the **first 10 kg**, **+2 mL/kg/hr** for kg **11–20**, **+1 mL/kg/hr** for each kg **>20**. **Daily volume** = hourly × 24, or use daily equivalents **100 / 50 / 20 mL/kg/day** per tier. Example **25 kg**: (10×4)+(10×2)+(5×1) = **65 mL/hr** → **1,560 mL/day**. Enter weight in the calculator above for step-by-step arithmetic and age-specific notes.

What is the Holliday-Segar method?

Published by **Holliday and Segar (1957)**, the method estimates **maintenance water** for patients who cannot drink—replacing urine (~60%), stool, and **insensible** losses. The **4-2-1** mnemonic matches decreasing metabolic cost per kg as body size grows. It remains a **bedside standard** in pediatrics and is often applied to adults as a starting point, though adults may also use **25–30 mL/kg/day** or protocol caps (e.g. **≤150 mL/hr**).

How do you calculate maintenance fluids for a pediatric patient?

Use **actual body weight in kg** (preterm/neonate protocols may differ day 1). **15 kg child**: 40 + (5×2) = **50 mL/hr** (**1,200 mL/day**). **8 kg infant**: 8×4 = **32 mL/hr**. Fluid choice is usually **isotonic dextrose-saline** per hospital policy (**D5 0.9% NaCl**). Add **KCl ~20 mEq/L** after **urine output** is established. Replace **emesis/NG/diarrhea** losses on top of maintenance. Reassess **q8–12 h** with exam, weight, and electrolytes.

What maintenance fluid rate for a 25 kg child?

**25 kg** → 40 (first 10 kg) + 20 (second 10 kg) + 5 (remaining 5 kg × 1) = **65 mL/hr**, **1,560 mL/24 h**. This matches the default demo on this page. Rates assume **euvolemia** and normal losses—**fever** often adds **~10% per °C >37**, and **ongoing losses** are replaced separately.

What IV fluids are used for maintenance (not boluses)?

Common choices: **D5 0.9% NaCl** (isotonic maintenance, reduces **hospital-acquired hyponatremia** risk vs hypotonic alone in many guidelines), **D5 0.45% NaCl** (traditional pediatric fluid—monitor **Na+**), or **balanced crystalloid** per protocol. **D5W alone** without electrolytes is rarely sufficient long term. **Potassium** typically **20 mEq/L** once **K+** safe and **UOP** adequate. **LR** may be used when chloride or acid-base concerns exist—follow local formulary.

When should you adjust maintenance fluid rates?

Increase for **fever** (~10% per °C above 37), **tachypnea**, **high ambient temperature**, and **measurable losses** (vomit, NG output, diarrhea). **Decrease** for **SIADH**, **heart failure**, **renal failure**, **post-op fluid restriction**, or **oliguria**—calculated maintenance may be excessive. **Neonates day 1** often start below full 4-2-1 and ramp per nursery protocol. **Obese adults**: consider **ideal body weight** so 4-2-1 does not over-prescribe volume.

What is the difference between maintenance and resuscitation fluids?

**Maintenance** = steady **hourly** infusion replacing **normal** losses in a **stable** NPO patient. **Resuscitation** = **boluses** (e.g. **10–20 mL/kg** isotonic) for **shock**, **severe dehydration**, or **acute deficit**. After hemodynamic stabilization, transition to **maintenance** plus **deficit replacement** and **ongoing loss** replacement as separate math. This calculator does **not** compute bolus volumes—use a **dehydration** or **sepsis** protocol tool.

What is the maximum maintenance fluid rate for adults?

Many services **cap** maintenance near **100–150 mL/hr** even if 4-2-1 exceeds that (e.g. **100 kg** → 4-2-1 = **140 mL/hr**). Alternative: **25–30 mL/kg/day** using **ideal body weight** in obesity (**70 kg IBW** → ~**1,750–2,100 mL/day** ≈ **73–88 mL/hr**). This page caps **adolescent/adult** selection at **150 mL/hr** for teaching—always follow **institutional policy**.

How do you monitor maintenance IV fluid therapy?

Track **intake vs output (I&O)** daily, **urine output** target often **0.5–2 mL/kg/hr** (lower acceptable in neonates per unit policy), **daily weight** (unexpected gain → fluid overload; loss → dehydration), **vitals**, **exam** (mucous membranes, cap refill, edema), and **serum Na+, K+, Cl−, glucose, BUN/Cr** every **12–24 h** until stable. Adjust rate when **Na** drifts, **UOP** sustained low, or **clinical status** changes.

Are there special fluid rules for neonates?

**Yes.** **Day 1** term neonates often receive **60–80 mL/kg/day**, increasing toward **140–160 mL/kg/day** by **day 7**—not always full Holliday-Segar on birth day. **Preterm** infants have **higher insensible losses** and may need **180–200 mL/kg/day** under NICU protocols. The calculator still shows **4-2-1 math** for weight but displays **neonate warnings**—always use **NICU/nursery orders**.

How does fever change maintenance fluid requirements?

Teaching rule: increase maintenance by **~10% for each 1°C** body temperature **above 37°C** (or ~12% per °F above 98.6) because insensible losses rise. Example: baseline **65 mL/hr** at 38°C → ~**71.5 mL/hr** (+10%). **Antipyretics** and **source control** also matter. Fever adjustment is **in addition to** replacing measured **NG/emesis** losses.

Is this maintenance fluid calculator medical advice?

**No.** It applies **Holliday-Segar arithmetic** for education. **Prescribing** requires licensed clinicians, **institutional IV fluid protocols**, and individual assessment. **Electrolyte disorders**, **DKA**, **renal replacement**, and **TPN** need specialized orders—not this page alone.

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IV fluids & pediatrics

Maintenance Fluid Calculator

Calculate maintenance IV fluid rate (mL/hr) and 24-hour volume from weight using the Holliday-Segar 4-2-1 rule. For pediatric maintenance fluids, neonate notes, and adult caps—not bolus resuscitation. More on our medical calculators hub.

Last updated: June 4, 2026

4-2-1 hourly rate with full calculation string

kg or lbs · neonate / child / adult guidance

Fever, fluid type, and monitoring teaching

Maintenance fluid calculator

Holliday-Segar 4-2-1 hourly rate and 24-hour volume

Body weight

Weight unit

Age group (guidance)

Fluid requirements

Maintenance rate

65 mL/hr

24-hour volume

1,560 mL/day

Calculation

40 + 20 + 5.0 kg × 1 mL/kg/hr = 65.0 mL/hr

Standard maintenance for 25.0 kg using the 4-2-1 rule (Holliday-Segar).

•Use isotonic maintenance fluid per hospital policy (often D5 0.9% NaCl).
•Add KCl ~20 mEq/L after adequate urine output and normal potassium.
•Replace ongoing losses (emesis, diarrhea) in addition to maintenance.
•Reassess rate every 8–12 h with exam, UOP, and electrolytes.

Maintenance only—not bolus resuscitation. Adjust for losses, fever, and renal/cardiac status per protocol.

Maintenance only. Do not use for shock boluses, DKA protocols, or deficit replacement without separate calculations. Verify with your hospital IV fluid policy.

Example rates (from calculator logic)

25 kg child

65 mL/hr

1,560 mL/day

8 kg infant

32 mL/hr

15 kg child

50 mL/hr

70 kg adult

110 mL/hr

4-2-1; may compare to 25–30 mL/kg/day

Holliday-Segar 4-2-1 rule (tiers)

Weight segment	Hourly	Daily equivalent	Example
First 10 kg	4 mL/kg/hr	100 mL/kg/day	8 kg → 32 mL/hr (768 mL/day)
Second 10 kg (11–20 kg)	+2 mL/kg/hr	+50 mL/kg/day	Adds to first tier (e.g. 15 kg → 50 mL/hr)
Each kg > 20 kg	+1 mL/kg/hr	+20 mL/kg/day	25 kg → 65 mL/hr; 30 kg → 70 mL/hr

Weight-based examples (mL/hr × 24 = mL/day)

Weight	mL/hr	mL/day	Note
8 kg	32	768	All weight in first tier
15 kg	50	1,200	40 + (5×2)
25 kg	65	1,560	40 + 20 + (5×1)
30 kg	70	1,680	40 + 20 + (10×1)
70 kg	110	2,640	Adult 4-2-1; may cap in tool

Maintenance vs resuscitation fluids

Aspect	Maintenance	Resuscitation
Purpose	Replace normal daily urine, stool, and insensible losses	Correct hypovolemia, shock, or large deficits quickly
Rate	Steady mL/hr (e.g. 50–65 mL/hr for 15–25 kg child)	Bolus 10–20 mL/kg over minutes—protocol specific
This tool	Holliday-Segar 4-2-1 only	Use separate dehydration/shock algorithms

Common maintenance IV fluids (teaching)

Fluid	Typical use
D5 0.9% NaCl (isotonic dextrose-saline)	Common maintenance in many hospitals; lowers hyponatremia risk vs hypotonic alone
D5 0.45% NaCl (half-normal + dextrose)	Traditional pediatric maintenance; monitor sodium
Balanced crystalloid (e.g. LR)	When chloride load or acid-base balance is a concern—follow protocol
Potassium	Typically 20 mEq/L after urine output confirmed and K+ safe

When to adjust the calculated rate

Fever:+10% maintenance per °C above 37 (or ~12% per °F above 98.6) — teaching rule
Vomiting / NG losses:Replace measured output (mL for mL) plus maintenance
Diarrhea:Replace stool losses per protocol; stool volume often estimated
Tachypnea / burns:Increased insensible losses—individualize
SIADH / heart failure / renal failure:Often restrict below calculated maintenance—specialist guidance

How maintenance fluid math works

Hourly mL/hr = 4×(first 10 kg) + 2×(kg 11–20) + 1×(kg >20)

Daily mL/day = hourly × 24

References

Holliday MA, Segar WE. Pediatrics. 1957The maintenance need for water in parenteral fluid therapy—origin of the 4-2-1 rule.
NICE NG29 — Intravenous fluid therapy in adultsPrinciples for maintenance vs resuscitation and fluid types.
AAP / pediatric hospital protocolsIsotonic maintenance and hyponatremia prevention themes.

For dehydration boluses and deficit math, see our pediatric dehydration calculator.

Worked example

25 kg child — default demo

Holliday-Segar step-by-step

40 + 20 + 5.0 kg × 1 mL/kg/hr = 65.0 mL/hr

Rate: 65 mL/hr · 24 h: 1,560 mL

Standard maintenance for 25.0 kg using the 4-2-1 rule (Holliday-Segar).

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IV fluids & pediatrics

Maintenance Fluid Calculator

Last updated: June 4, 2026

4-2-1 hourly rate with full calculation string

kg or lbs · neonate / child / adult guidance

Fever, fluid type, and monitoring teaching

Maintenance fluid calculator

Holliday-Segar 4-2-1 hourly rate and 24-hour volume

Body weight

Weight unit

Age group (guidance)

Fluid requirements

Maintenance rate

65 mL/hr

24-hour volume

1,560 mL/day

Calculation

40 + 20 + 5.0 kg × 1 mL/kg/hr = 65.0 mL/hr

Standard maintenance for 25.0 kg using the 4-2-1 rule (Holliday-Segar).

•Use isotonic maintenance fluid per hospital policy (often D5 0.9% NaCl).
•Add KCl ~20 mEq/L after adequate urine output and normal potassium.
•Replace ongoing losses (emesis, diarrhea) in addition to maintenance.
•Reassess rate every 8–12 h with exam, UOP, and electrolytes.

Maintenance only—not bolus resuscitation. Adjust for losses, fever, and renal/cardiac status per protocol.

Maintenance only. Do not use for shock boluses, DKA protocols, or deficit replacement without separate calculations. Verify with your hospital IV fluid policy.

Example rates (from calculator logic)

25 kg child

65 mL/hr

1,560 mL/day

8 kg infant

32 mL/hr

15 kg child

50 mL/hr

70 kg adult

110 mL/hr

4-2-1; may compare to 25–30 mL/kg/day

Holliday-Segar 4-2-1 rule (tiers)

Weight segment	Hourly	Daily equivalent	Example
First 10 kg	4 mL/kg/hr	100 mL/kg/day	8 kg → 32 mL/hr (768 mL/day)
Second 10 kg (11–20 kg)	+2 mL/kg/hr	+50 mL/kg/day	Adds to first tier (e.g. 15 kg → 50 mL/hr)
Each kg > 20 kg	+1 mL/kg/hr	+20 mL/kg/day	25 kg → 65 mL/hr; 30 kg → 70 mL/hr

Weight-based examples (mL/hr × 24 = mL/day)

Weight	mL/hr	mL/day	Note
8 kg	32	768	All weight in first tier
15 kg	50	1,200	40 + (5×2)
25 kg	65	1,560	40 + 20 + (5×1)
30 kg	70	1,680	40 + 20 + (10×1)
70 kg	110	2,640	Adult 4-2-1; may cap in tool

Maintenance vs resuscitation fluids

Aspect	Maintenance	Resuscitation
Purpose	Replace normal daily urine, stool, and insensible losses	Correct hypovolemia, shock, or large deficits quickly
Rate	Steady mL/hr (e.g. 50–65 mL/hr for 15–25 kg child)	Bolus 10–20 mL/kg over minutes—protocol specific
This tool	Holliday-Segar 4-2-1 only	Use separate dehydration/shock algorithms

Common maintenance IV fluids (teaching)

Fluid	Typical use
D5 0.9% NaCl (isotonic dextrose-saline)	Common maintenance in many hospitals; lowers hyponatremia risk vs hypotonic alone
D5 0.45% NaCl (half-normal + dextrose)	Traditional pediatric maintenance; monitor sodium
Balanced crystalloid (e.g. LR)	When chloride load or acid-base balance is a concern—follow protocol
Potassium	Typically 20 mEq/L after urine output confirmed and K+ safe

When to adjust the calculated rate

Fever:+10% maintenance per °C above 37 (or ~12% per °F above 98.6) — teaching rule
Vomiting / NG losses:Replace measured output (mL for mL) plus maintenance
Diarrhea:Replace stool losses per protocol; stool volume often estimated
Tachypnea / burns:Increased insensible losses—individualize
SIADH / heart failure / renal failure:Often restrict below calculated maintenance—specialist guidance

How maintenance fluid math works

Hourly mL/hr = 4×(first 10 kg) + 2×(kg 11–20) + 1×(kg >20)

Daily mL/day = hourly × 24

References

Holliday MA, Segar WE. Pediatrics. 1957The maintenance need for water in parenteral fluid therapy—origin of the 4-2-1 rule.
NICE NG29 — Intravenous fluid therapy in adultsPrinciples for maintenance vs resuscitation and fluid types.
AAP / pediatric hospital protocolsIsotonic maintenance and hyponatremia prevention themes.

For dehydration boluses and deficit math, see our pediatric dehydration calculator.