- Enter the patient's body weight in kg. The calculator accepts any weight >0 kg.
- The result displays both the daily volume (mL/day) via the Holliday-Segar formula and the hourly rate (mL/hr) via the 4-2-1 rule.
- Review the clinical notes in the result box — Holliday-Segar was derived in children; adult targets and fluid selection differ from the formula output.
- Consult the IV Fluid Compositions table below the calculator to choose the appropriate fluid type (tonicity, electrolytes, buffer).
- Adjust the rate for clinical context: fever, ongoing losses, AKI, heart failure, or cirrhosis all require individualized targets.
All computation runs in your browser; no values are stored or transmitted.
When to Use
Use this calculator to estimate the starting maintenance IV fluid rate for a patient who cannot take fluids orally or enterally, or as a reference when checking an existing infusion order. The Holliday-Segar formula and 4-2-1 rule provide a weight-based starting point that must then be individualized to the clinical context — they are not fixed prescriptions.
Appropriate uses
- Estimating maintenance fluid needs in pediatric patients (the population the formula was originally validated in).
- Providing an initial rate for adults who are nil per os (NPO) for procedures, as a starting point before clinical adjustment.
- Cross-checking a prescribed fluid order against weight-based targets.
- Educational reference for fluid management principles alongside the IV fluid compositions table.
Limitations and cautions
- Adults: Holliday-Segar often over-estimates adult maintenance needs. A common adult target is 25–30 mL/kg/day; rates are often capped at ~2400 mL/day.
- Fluid type matters: Current guidance (NICE CG174; Moritz & Ayus) strongly favors isotonic maintenance fluids in most patients to prevent iatrogenic hyponatremia — do not use hypotonic saline (0.45% NaCl, D5W) as default maintenance without careful electrolyte monitoring.
- Adjust for losses: This calculator estimates insensible-only maintenance. Add replacement for ongoing losses (surgical drains, GI losses, fever) separately.
- Contraindicated in volume-overloaded states: Do not apply formula targets to patients with pulmonary edema, anuria/oliguria, or severe heart failure without specialist guidance.
Pearls & Pitfalls
Use isotonic fluids for maintenance
NICE CG174 (2013/2017) and Moritz & Ayus (NEJM 2015) demonstrate that hypotonic fluids cause hospital-acquired hyponatremia — a preventable harm. Unless a specific indication exists (e.g., hypernatremia correction), maintenance IV fluids should be isotonic (0.9% NaCl or a balanced crystalloid such as Lactated Ringer's or Plasma-Lyte 148). Add potassium and glucose as appropriate to the clinical situation.
Adult maintenance is different from pediatric
Holliday-Segar was derived from metabolic data in hospitalized children in 1957. In adults, the formula frequently yields rates higher than physiological need, especially in sedentary, post-operative, or critically ill patients. Many adult protocols cap maintenance at 1.5–2.0 L/day or 25–30 mL/kg/day. Use the formula output as a ceiling estimate, not a target, in adult patients.
Pitfalls to avoid
- Do not use the formula rate unchanged in oliguric AKI, severe heart failure, or cirrhosis with ascites — volume status must guide therapy in these patients.
- Do not use 0.45% NaCl ("half-normal") or D5W as routine maintenance — the risk of hyponatremia is well documented.
- Do not confuse maintenance fluids with resuscitation fluids — this calculator estimates maintenance only, not bolus resuscitation requirements.
- Fever increases insensible losses approximately 10–15% per degree Celsius above 37°C; adjust accordingly.
Why Use It
Appropriate maintenance fluid therapy prevents both dehydration and fluid overload — two common iatrogenic complications in hospitalized patients. A weight-based starting point ensures that very small or very large patients receive proportionate initial rates, which are then refined with clinical monitoring. The accompanying IV fluid composition table helps clinicians rapidly select the most physiologically appropriate fluid, a decision that affects sodium balance, acid-base status, and the risk of adverse electrolyte events.
Maintenance IV Fluid Calculator — Holliday-Segar / 4-2-1 Rule
Enter the patient's body weight in kilograms. The calculator will display the estimated daily volume (Holliday-Segar) and hourly infusion rate (4-2-1 rule), with clinical context notes.
⚕ Holliday-Segar daily volume: ≤10 kg → 100 mL/kg; 10–20 kg → 1000 + 50 mL/kg above 10; >20 kg → 1500 + 20 mL/kg above 20. 4-2-1 hourly rate: ≤10 kg → 4 mL/kg/hr; 10–20 kg → 40 + 2 mL/kg/hr above 10; >20 kg → 60 + 1 mL/kg/hr above 20. Originally validated in children; adult maintenance is commonly capped at ~2400 mL/day (25–30 mL/kg/day). Fluid selection requires clinical judgment — see the composition table below. Requires physician review before prescribing.
IV Fluid Classification & Compositions
Plasma osmolarity reference ≈ 285–295 mOsm/L. Values are approximate and per litre; confirm against the product label.
Crystalloids — Isotonic
| Fluid | Composition (per L, approx.) | Tonicity / Osm (mOsm/L) | Common uses |
|---|---|---|---|
| 0.9% NaCl (Normal Saline, NSS) | Na 154, Cl 154 | Isotonic · ~308 | Hypovolemia, shock, hyponatremia, with blood transfusions |
| Lactated Ringer's (Hartmann's) | Na 130, K 4, Ca 2.7, Cl 109, lactate 28 | Isotonic · ~273 | Sepsis, trauma, surgery, dehydration |
| Plasma-Lyte 148 | Na 140, K 5, Mg 3, Cl 98, acetate 27, gluconate 23 | Isotonic · ~295 | Sepsis, critical care, perioperative fluid |
| Ringer's solution (no lactate) | Na 147, K 4, Ca 4.5, Cl 156 | Isotonic · ~309 | Volume replacement |
Crystalloids — Hypotonic
| Fluid | Composition (per L, approx.) | Tonicity / Osm (mOsm/L) | Common uses |
|---|---|---|---|
| 0.45% NaCl (½ NS) | Na 77, Cl 77 | Hypotonic · ~154 | Hypernatremia, maintenance (free water) |
| 0.33% NaCl | Na 56, Cl 56 | Hypotonic · ~111 | Pediatric maintenance (less common) |
| 0.225% NaCl (¼ NS) | Na 38, Cl 38 | Hypotonic · ~77 | Specialized pediatric use (usually with dextrose) |
Dextrose-containing
| Fluid | Composition (per L, approx.) | Tonicity / Osm (mOsm/L) | Common uses |
|---|---|---|---|
| 5% Dextrose in Water (D5W) | Dextrose 50 g | ~252 — isotonic in bag, effectively hypotonic after metabolism | Free water replacement, drug dilution |
| 10% Dextrose in Water (D10W) | Dextrose 100 g | Hypertonic · ~505 | Hypoglycemia, neonatal care |
| 50% Dextrose (D50) | Dextrose 500 g | Hypertonic · ~2525 | Severe hypoglycemia, hyperkalemia protocol (with insulin) |
| D5 0.9% NaCl (D5NS) | Dextrose 50 g + Na 154, Cl 154 | Hypertonic · ~560 | Maintenance with sodium replacement |
| D5 0.45% NaCl | Dextrose 50 g + Na 77, Cl 77 | Hypertonic · ~406 | Maintenance fluids |
| D5 Lactated Ringer's | Dextrose 50 g + LR electrolytes | Hypertonic · ~525 | Postoperative maintenance |
| D5NM (Dextrose 5% + maintenance electrolytes) | Dextrose 50 g + Na ~40, K ~13, Mg, acetate (Normosol-M type) | Hypertonic | Daily maintenance |
| D5NR (Dextrose 5% + balanced electrolytes) | Dextrose 50 g + Na ~140, K ~5, Mg, acetate/gluconate (Normosol-R type) | Hypertonic | Maintenance / replacement |
Colloids
| Fluid | Composition | Common uses |
|---|---|---|
| Human Albumin 5% | 50 g/L albumin, iso-oncotic | Volume expansion |
| Human Albumin 25% | 250 g/L albumin, hyper-oncotic | Hypoalbuminemia, cirrhosis (large-volume paracentesis / SBP), dialysis support |
| Dextran 40 | Low-molecular-weight glucose polymer | Rarely used |
| Dextran 70 | Higher-molecular-weight dextran | Rarely used |
| Gelatin solution | Gelatin-based colloid | Volume expansion (where available) |
* Lactated Ringer's osmolarity is 273 mOsm/L (mildly below plasma), but it is considered physiologically isotonic due to protein-binding effects of lactate in vivo. D5 Half-NS osmolarity of ~406 mOsm/L is in-bag; after dextrose metabolism it is effectively hypotonic. Plasma osmolarity reference: 285–295 mOsm/L.
Next Steps
Use the result as a starting point, not a fixed prescription.
- Individualize the rate for clinical context: volume status, ongoing losses (fever, surgical drains, vomiting, diarrhea), urine output, comorbidities (AKI, heart failure, cirrhosis, SIADH).
- Monitor daily: weight, fluid balance (ins vs. outs), serum electrolytes (Na, K, Cl, HCO₃), renal function, and clinical signs of overload or dehydration.
- Choose the fluid type from the composition table: prefer isotonic (balanced crystalloid or 0.9% NaCl) for most maintenance; add KCl and glucose as appropriate.
- Reassess and adjust the rate at each clinical review; avoid fixed-rate orders that persist beyond 24 hours without reassessment.
- Transition to oral/enteral hydration as soon as clinically feasible — IV maintenance fluids are a bridge, not a long-term solution.
- Consult nephrology or critical care for patients with complex fluid-electrolyte disturbances, AKI, or severe heart failure.
Evidence & References
Formula
| Quantity | Rule | Formula |
|---|---|---|
| Daily volume (mL/day) | Holliday-Segar | ≤10 kg: 100 × weight; 10–20 kg: 1000 + 50 × (wt − 10); >20 kg: 1500 + 20 × (wt − 20) |
| Hourly rate (mL/hr) | 4-2-1 Rule | ≤10 kg: 4 × weight; 10–20 kg: 40 + 2 × (wt − 10); >20 kg: 60 + 1 × (wt − 20) |
| Adult maintenance target | NICE CG174 | 25–30 mL/kg/day; typical adult cap ~2000–2500 mL/day |
References
- Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823–832.
- Moritz ML, Ayus JC. Maintenance intravenous fluids in acutely ill patients. N Engl J Med. 2015;373(14):1350–1360.
- National Institute for Health and Care Excellence (NICE). Intravenous fluid therapy in adults in hospital (CG174). 2013 (updated 2017).
