Fluid Deficit Calculator

The calculator maps broad severity selections to assumed weight-loss percentages and estimates deficit volume in mL. Clinical dehydration categories are not reliably diagnosed from a calculator or one sign, and a pre-illness weight may be unavailable. Age, cause, electrolytes, circulation, urine output, and ongoing losses all change management. Severe symptoms, lethargy, poor perfusion, or inability to drink need urgent medical care.

Holliday-Segar is a historical weight-based estimate of pediatric maintenance needs: 100 mL/kg/day for the first 10 kg, 50 mL/kg/day for the next 10 kg, and 20 mL/kg/day above 20 kg. This calculator shows that estimate separately from the modeled deficit. It also divides the deficit by 24 as arithmetic only. It does not choose an IV fluid or rate, and it does not account for electrolytes, renal or cardiac disease, fluid restriction, resuscitation needs, ongoing losses, or a replacement schedule. Use a current clinical protocol for patient care.

Children, and infants especially, have a narrower margin for fluid error than adults. Total body water is a larger fraction of body weight, renal concentrating ability is still developing, and blood pressure may stay normal until shock is advanced. Overcorrection can also cause serious harm. Pediatric fluid selection, dose, timing, and monitoring require direct clinical assessment and a current pediatric protocol.

Fluid selection depends on the cause of dehydration, age, electrolytes, glucose, kidney and cardiac function, neurologic injury, medications, and local protocol. Balanced crystalloids and 0.9 percent saline are both used in different settings, and current protocols do not support a universal choice from this calculator. Do not use the output to choose an IV fluid or rate for patient care.

This calculator is educational only and is not a substitute for medical advice, emergency care, or local clinical protocols. Seek urgent clinical help for shock, severe dehydration with altered mental status, acute kidney injury, dangerous sodium or potassium abnormalities, ongoing losses that outpace replacement, pulmonary edema or hypoxia during fluids, or high-risk patients with CHF, cirrhosis, advanced CKD, or infancy. Clinicians should follow local escalation pathways and involve pediatric, ICU, emergency, or specialty teams when protocol criteria are met.