Osmolal Gap Calculator

Enter Na (mEq/L), glucose and BUN (mg/dL), optional ethanol, and the measured osmolality.

Sodium (Na⁺), mEq/L:

Glucose, mg/dL:

BUN, mg/dL:

Ethanol, mg/dL (optional):

Measured osmolality, mOsm/kg:

Calc = 2×Na + Glu/18 + BUN/2.8 + EtOH/3.7. Gap = Measured − Calc.

Gap ≥ 10 mOsm/kg is often considered elevated; correlate clinically.