Calculated Serum Osmolality & Toxic Alcohol Osmolal Gap Calculator

Compute calculated serum osmolality (mOsm/kg) and osmolal gap.

Calculated Serum Osmolality
290.28 mOsm/kg
Serum Osmolal Gap (Measured − Calc) 7.72 mOsm/kg
Effective Osmolality (Tonicity = 2·Na + Glu/18) 285.28 mOsm/kg
Urea Osmolality Contribution (BUN/2.8) 5 mOsm/kg
Inputs
⚡ Scenarios:
mEq/L
Serum Sodium in mEq/L.
mg/dL
Serum Glucose in mg/dL.
mg/dL
Blood Urea Nitrogen (BUN) in mg/dL.
mOsm/kg
Measured freezing-point serum osmolality (mOsm/kg).
Results & Graph
Calculated Serum Osmolality
290.28 mOsm/kg
Serum Osmolal Gap (Measured − Calc)
7.72 mOsm/kg
Effective Osmolality (Tonicity = 2·Na + Glu/18)
285.28 mOsm/kg
Urea Osmolality Contribution (BUN/2.8)
5 mOsm/kg

Calculated Serum Osmolality

Graph 1 • Serum Osmolality & Gap • Domain Architecture & Live Telemetry Maps Serum Sodium Meq L, Serum Glucose Mg Dl, Serum Bun Mg Dl through Serum Osmolality & Gap Formula.
Serum Osmolality & Gap • Clinical & Physiological Reference Scale Low / Baseline Target / Reference Elevated / Watch High / Action Calculated Serum Osmolality: 290.28 mOsm/kg Serum Osmolal Gap (Measure 7.72 mOsm/kg Effective Osmolality (Toni 285.28 mOsm/kg Urea Osmolality Contributi 5 mOsm/kg
Graph 2 • Calculated Serum Osmolality Across Serum Sodium Meq L Sweep (40% → 160%) Evaluates CalcOsm = 2 × Na + (Glucose / 18) + (BUN / 2.8) + (Ethanol_mg_dL / 3.7); across 7 operating points (current input highlighted).
0 mOsm/k 252.1 mOsm/k 504.1 mOsm/k 122.3 56mEq/L 178.3 84mEq/L 234.3 112mEq/L 290.3 140mEq/L 346.3 168mEq/L 402.3 196mEq/L 458.3 224mEq/L
Graph 3 • Joint Sensitivity: Serum Sodium Meq L × Serum Glucose Mg Dl Compares Calculated Serum Osmolality when Serum Glucose Mg Dl is shifted +25% (solid) vs. −25% (dashed).
0 mOsm/k 206.6 mOsm/k 413.2 mOsm/k --- Serum Glucose Mg Dl @ 75% 207.6 -30% 249.6 -15% 291.6 +0% 333.6 +15% 375.6 +30%
Summary: Calculated osmolality is 290.3 mOsm/kg vs. 298 mOsm/kg measured, yielding an Osmolal Gap of 7.7 mOsm/kg (Normal ≤10 mOsm/kg).
Summary: Calculated osmolality is 290.3 mOsm/kg vs. 298 mOsm/kg measured, yielding an Osmolal Gap of 7.7 mOsm/kg (Normal ≤10 mOsm/kg).
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Interactive chart & math engine powered by CalculatorGraph

Formula & Mathematical Methodology: Serum Osmolality & Gap Formula

CalcOsm = 2 × Na + (Glucose / 18) + (BUN / 2.8) + (EthanolmgdL / 3.7)
OsmolalGap = MeasuredOsm − CalcOsm
CalcOsm = 2 × Na + (Glucose / 18) + (BUN / 2.8) + (Ethanol_mg_dL / 3.7); OsmolalGap = MeasuredOsm − CalcOsm
  • serumSodiumMeqL: Serum Sodium Meq L (mEq/L)
  • serumGlucoseMgDl: Serum Glucose Mg Dl (mg/dL)
  • serumBunMgDl: Serum Bun Mg Dl (mg/dL)
  • measuredLabOsmolality: Measured Lab Osmolality (mOsm/kg)

Rounding: Clinical scores round to statutory integer or decimal precision; physiological metrics round to 2 decimal places.

Worked Example: Clinical / Physiology Scenario: Serum Osmolality & Gap

Compute calculated serum osmolality (mOsm/kg) and osmolal gap.

  1. Enter lab values, anthropometric measurements, or performance test metrics.
  2. Evaluate the reference equation: CalcOsm = 2 × Na + (Glucose / 18) + (BUN / 2.8) + (Ethanol_mg_dL / 3.7); OsmolalGap = MeasuredOsm − CalcOsm.
  3. Inspect the primary classification, supporting indices, and 3 SVG charts.
Result: Computes Serum Osmolality & Gap via CalcOsm = 2 × Na + (Glucose / 18) + (BUN / 2.8) + (Ethanol_mg_dL / 3.7); OsmolalGap = MeasuredOsm − CalcOsm.

Frequently Asked Questions

How does the Calculated Serum Osmolality & Toxic Alcohol Osmolal Gap Calculator compute its result?

It evaluates CalcOsm = 2 × Na + (Glucose / 18) + (BUN / 2.8) + (Ethanol_mg_dL / 3.7); OsmolalGap = MeasuredOsm − CalcOsm directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to solve backwards for a target lab value or pace?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any numeric input parameter.

Are my health and biometric inputs kept private?

Yes. All calculations run 100% locally on your device with zero external transmission.

Health & Fitness · Clinical Nephrology & Electrolytes

Calculated Serum Osmolality & Toxic Alcohol Osmolal Gap Calculator: inputs, method, and how to read the result

Compute calculated serum osmolality (mOsm/kg) and osmolal gap.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Serum Sodium Meq L: Serum Sodium in mEq/L.
  • Serum Glucose Mg Dl: Serum Glucose in mg/dL.
  • Serum Bun Mg Dl: Blood Urea Nitrogen (BUN) in mg/dL.
  • Measured Lab Osmolality: Measured freezing-point serum osmolality (mOsm/kg).

What the calculation includes

With the default values shown, Calculated Serum Osmolality is 290.28 mOsm/kg. The calculation follows Serum Osmolality & Gap Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Serum Sodium Meq L from 140 mEq/L to 154 mEq/L changes Calculated Serum Osmolality from 290.28 mOsm/kg to 318.28 mOsm/kg. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses peer-reviewed clinical and sports physiology formulas.
  • For educational and informational reference only; clinical scores do not replace physician judgment or laboratory reference ranges.

Scope: Global Clinical & Sports Science Consensus Check the assumptions and limitations against your situation before relying on the estimate.

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