Calculator

Enter measured sodium and glucose, then choose glucose units. Selecting SI units applies to both sodium and glucose (same as the original calculator).

Units follow the selection below (mEq/L or mmol/L).
Units follow the selection below (mg/dL or mmol/L).
Sodium units
Kept in sync with glucose units (original behavior).
Glucose units
Kept in sync with sodium units (original behavior).
Effective osmolality excludes urea (BUN).
Formulas (as used by this calculator)

Glucose in mg/dL
Katz: Corrected Na = Na + 0.016 × (glucose − 100)
Hillier: Corrected Na = Na + 0.024 × (glucose − 100)
Effective serum osmolality = 2 × Na + (glucose / 18)

Glucose in mmol/L
Katz: Corrected Na = Na + 1.6 × ((glucose − 5.5) / 5.5)
Hillier: Corrected Na = Na + 2.4 × ((glucose − 5.5) / 5.5)
Effective serum osmolality = 2 × Na + glucose

Disclaimer: All calculations must be confirmed before use. The suggested results are not a substitute for clinical judgment. Neither Perinatology.com nor any other party involved in the preparation or publication of this site shall be liable for any special, consequential, or exemplary damages resulting in whole or part from use of this material.
Updated 12/21/2025 by Mark A Curran, MD, FACOG.