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Osmolal Gap Calculator

Calculate osmolal gap with clear inputs, formulas, and supporting results.

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Osmolal Gap

Osmolal Gap Calculator

Osmolal gap—
Calculated osmolality—
Results are estimates for informational purposes. Verify critical calculations and project requirements independently.

Calculator Inputs and Outputs

Inputs

  • Measured serum osmolality (mOsm/kg) — example: 300
  • Sodium (mEq/L) — example: 140
  • Glucose (mg/dL) — example: 100
  • BUN (mg/dL) — example: 14
  • Ethanol (mg/dL) — example: 0

Results

  • Osmolal gap (mOsm/kg)
  • Calculated osmolality (mOsm/kg)

Formula used

Calculated osmolality = 2Na + glucose/18 + BUN/2.8 + ethanol/4.6; gap = measured − calculated.

How to Use the Osmolal Gap Calculator

Enter the requested values, check the units and assumptions, then select Calculate Osmolal Gap. The built-in defaults provide a complete working example.

Formula

Calculated osmolality = 2Na + glucose/18 + BUN/2.8 + ethanol/4.6; gap = measured − calculated.

Understanding the Results

The primary answer appears first. Supporting outputs show related quantities, conversions, dates, costs, ratios, or intermediate values. Calculations keep additional precision before display rounding.

Accuracy Tips

  • Use measured values and consistent units.
  • Review assumptions, rates, timing, and efficiency inputs.
  • Recalculate after changing any condition.

Important Note

This tool provides an informational estimate. Confirm critical financial, medical, construction, scientific, tax, legal, or safety decisions with an appropriately qualified professional.

Calculation Standards

This tool uses documented formulas and high-precision internal values. Displayed results may be rounded for readability. Review the assumptions and verify important decisions with a qualified professional.

Read our calculation methodology