Dehydration Correction Calculator

All calculations should be independently verified prior to clinical use. These calculators are intended to supplement, not replace, clinical judgment.

Calculate intravenous fluids required to correct isonatremic, hyponatremic, or hypernatremic dehydration, including maintenance and deficit components.

Before using this calculator: Correct shock and treat hyponatremic seizures before initiating dehydration correction. Consider ongoing losses and replace as appropriate. Exercise caution with large and non-pediatric patients. This calculator is intended for pediatric use based on the Harriet Lane Handbook method.

Baseline weight kg

Dehydrated weight kg or %

Serum Na⁺ mEq/L

Replacement interval hr

Fluid Schedule

Phase	Duration	Na⁺	K⁺	Rate

Na⁺ and K⁺ are the required fluid concentrations in mEq/L. Select an IV fluid approximating the Na⁺ concentration, add KCl to match the K⁺ concentration, and infuse at the stated rate for the stated duration. Consider acetate or phosphate buffers as appropriate.

Maintenance fluids are calculated by the Holliday-Segar method (100 mL/kg/day for the first 10 kg, 50 mL/kg/day for the next 10 kg, 20 mL/kg/day thereafter). Maintenance sodium is 3 mEq/kg/day and maintenance potassium is 2 mEq/kg/day.

Deficit fluids equal the fluid deficit in mL (weight loss × 1000, or baseline weight × % dehydration × 10). For hypernatremic dehydration (Na⁺ > 150 mEq/L), the free-water deficit is calculated using the following formula with a target Na⁺ of 145 mEq/L:

FWD (L) = Wt (kg) × 0.6 × ( Na⁺_serum ÷ Na⁺_target − 1 )

The isotonic deficit is the total fluid deficit minus the free-water deficit (clamped to zero). Deficit Na⁺ (0.6 × 145 mEq/L) and deficit K⁺ (0.4 × 150 mEq/L) are applied only to the isotonic portion. If the free-water deficit exceeds the total deficit, the Hypernatremia Correction Calculator should be used to manage the remaining hypernatraemia after the dehydration is corrected.

Phasing: For isonatremic and hyponatremic dehydration, the first half of the deficit is replaced during the first third of the replacement interval; the second half over the remaining two-thirds. For hypernatremic dehydration, the entire fluid deficit plus 24 hr maintenance is replaced over 24 hours, after which, use the Hypernatremia Correction Calculator to treat any remaining hypernatremia.

Pick a fluid that approximates the desired Na⁺ concentration:

Solution	Concentration	Na⁺ (mEq/L)
NS	0.9% Saline	154
½ NS	0.45% Saline	77
⅓ NS	0.3% Saline	51
¼ NS	0.22% Saline	39
⅕ NS	0.2% Saline	30
⅙ NS	0.15% Saline	26
Lactated Ringer’s	—	130
3% Saline	Hypertonic	513
5% Saline	Hypertonic	856

References

Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823–832.
Custer JW, Rau RE, eds. The Harriet Lane Handbook. 18th ed. Mosby Elsevier; 2009.
Friedman AL. Pediatric hydration therapy: historical review and a new approach. Kidney Int. 2005;67(1):380–388.