Free Water Deficit Calculator

Sex

Male Female

Sex is required

Age Category

Child (<18) Adult (18-65) Elderly (≥65)

Age Category is required

Current Sodium Units

Current Sodium Level is required

Desired Sodium Units

mEq/L

Weight

Weight is required

Correction Factor Per Hour

mEq/L/h

Free Water Deficit

Total Hours to Correct (using D5W)

Rate Per Hour (using D5W)

Information/Conversions

Water Deficit = [(Age Sex Factor * Normal Weight) * (Serum Na - Desired Na)] / Desired Na

Age Sex Factor: 0.6 (male) or 0.5 (female). If elderly use, 0.5 (male) and 0.45 (female). If child use 0.6 for (male) and (female)

Using D5W, this calculation is based on a conservative correction rate of 0.5 mEq/L/h to avoid cerebral edema but the value can be changed. Patients should be carefully monitored for the rate of correction, urine output, and ongoing losses