2,500
mL/day
104.2
mL/hr
35.7
mL/kg/day
110
mL/hr
2,500
mL/day
104.2
mL/hr
35.7
mL/kg/day
110
mL/hr
The Fluid Maintenance Calculator determines the baseline intravenous fluid rate needed to replace normal daily water and electrolyte losses in patients who cannot maintain adequate oral intake. This calculation uses the Holliday-Segar formula, the most widely used method for estimating maintenance fluid requirements in both pediatric and adult patients. First published in 1957, this formula remains the standard of care in hospitals worldwide for prescribing maintenance IV fluids.
The Holliday-Segar formula is based on the observation that metabolic rate (and therefore water and electrolyte expenditure) is closely related to body weight but not in a linear fashion. The formula uses a tiered approach: 100 mL/kg/day for the first 10 kg of body weight, 50 mL/kg/day for the next 10 kg (11-20 kg), and 20 mL/kg/day for each additional kilogram above 20 kg. This tiered system reflects the higher metabolic rate per kilogram in smaller patients and the diminishing incremental fluid needs as body size increases.
Maintenance fluids serve to replace three categories of normal daily fluid losses: insensible losses (through skin and respiratory tract, approximately 30-50% of total), urinary losses (approximately 50-60% of total), and stool losses (approximately 5-10% of total). The Holliday-Segar formula was designed to approximate these combined losses for patients at rest in a temperate environment. Additional fluid beyond maintenance is needed for patients with increased losses from fever, burns, surgical drains, diarrhea, or other sources.
For adults weighing over 60-70 kg, the Holliday-Segar formula typically yields 2,400-2,600 mL/day, which aligns well with the general adult recommendation of 25-30 mL/kg/day. However, in practice, clinicians often cap adult maintenance fluids at approximately 2,500 mL/day or use simplified adult rates of 100-125 mL/hr. Obese patients present a challenge because using total body weight overestimates fluid needs — many clinicians use ideal body weight or an adjusted weight for obese patients.
This calculator provides the total daily volume, hourly infusion rate, and per-kilogram rate. While the Holliday-Segar formula is universally applied, the choice of specific maintenance fluid (isotonic vs hypotonic, with or without dextrose and potassium) depends on clinical context, patient age, and underlying conditions. Recent evidence favors isotonic fluids (normal saline or Ringer's lactate) over hypotonic solutions for most patients to reduce the risk of hospital-acquired hyponatremia. Always confirm fluid orders with the treating physician and adjust based on clinical response and laboratory monitoring.
The Holliday-Segar formula: First 10 kg: 100 mL/kg/day. Next 10 kg (11-20): 50 mL/kg/day. Each kg above 20: 20 mL/kg/day. Example for 70 kg: (10 x 100) + (10 x 50) + (50 x 20) = 1000 + 500 + 1000 = 2500 mL/day. Hourly rate = daily total / 24. Per-kg rate = daily total / body weight.
The calculated volume represents baseline maintenance for a patient at rest without abnormal losses. Add additional fluid for fever (+10-15% per degree C above 37), tachypnea, burns, surgical drains, diarrhea, or vomiting. Reduce for patients with heart failure, renal failure, or fluid overload risk. The hourly rate is useful for IV pump settings. Monitor urine output (target 0.5-1 mL/kg/hr in adults) as a guide for fluid adequacy.
Inputs
Results
A 70 kg adult needs 2500 mL/day maintenance fluid at 104 mL/hr.
Inputs
Results
A 15 kg child needs 1250 mL/day: (10x100) + (5x50) = 1250 mL.
The Holliday-Segar formula (1957) estimates daily maintenance fluid needs: 100 mL/kg for the first 10 kg, 50 mL/kg for the next 10 kg, and 20 mL/kg for each kg above 20. It is the most widely used method for calculating IV maintenance fluids.
The tiered approach reflects that metabolic rate per kilogram decreases with increasing body size. A 5 kg infant has proportionally higher metabolic needs per kg than a 70 kg adult. The 4-2-1 rule (mL/kg/hr equivalent) captures this relationship.
The 4-2-1 rule is the hourly equivalent of the Holliday-Segar formula: 4 mL/kg/hr for the first 10 kg, 2 mL/kg/hr for the next 10 kg, 1 mL/kg/hr above 20 kg. It gives the same daily total but is easier for hourly rate calculations.
Current evidence favors isotonic fluids (0.9% NaCl or balanced crystalloids) for most patients. Hypotonic maintenance fluids increase the risk of hyponatremia, especially in children. Dextrose (D5) is often added for children and fasting patients.
For significantly obese patients, using total body weight overestimates fluid needs. Many clinicians use ideal body weight or apply a correction factor. Discuss with the treating physician for patients with BMI above 30.
Increase for fever (+10-15% per degree above 37C), hyperventilation, or excessive losses (drains, diarrhea). Decrease for heart failure, renal impairment, SIADH, or hepatic failure with ascites. Always individualize based on clinical assessment.
Target urine output of 0.5-1 mL/kg/hr in adults, 1-2 mL/kg/hr in children. Monitor daily weights, intake and output records, serum electrolytes, and clinical signs of dehydration or fluid overload.
No. Maintenance fluids replace ongoing daily losses at a steady rate. Resuscitation fluids (boluses of 10-20 mL/kg) are given rapidly to restore intravascular volume in dehydrated or shocked patients. They serve different purposes.
Ideally, IV maintenance fluids are temporary until oral intake resumes. Prolonged IV fluids (over 48-72 hours) increase infection risk at the IV site and may cause electrolyte imbalances. Transition to oral intake as soon as clinically appropriate.
The Holliday-Segar formula can underestimate needs in neonates (especially premature infants) who have higher insensible losses. Neonatal fluid management uses specialized calculations based on gestational age, postnatal day, and weight. Consult neonatal guidelines.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
How helpful was this calculator?
Be the first to rate!
