Osmolality Calculator Suite
Calculate osmolality for clinical and laboratory applications
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General Osmolality Calculator
Solutes in Solution
| Solute | Concentration (mmol/kg) | Dissociation (i) | Contribution (mOsm/kg) | Action |
|---|---|---|---|---|
| NaCl | 150 | 2 | 300 | |
| Glucose | 5.5 | 1 | 5.5 |
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Measurement Conditions
Standard measurement at 25°C
Common Dissociation Factors
- • NaCl: i = 1.85 (practical) or 2 (theoretical)
- • KCl: i = 1.85
- • CaCl₂: i = 2.5-3
- • Glucose: i = 1
- • Urea: i = 1
Common Biological Solutes
General Calculator Info
Osmolality: Concentration of osmotically active particles per kg of solvent
Units: mOsm/kg H₂O (milliosmoles per kilogram of water)
Measurement: Measured by freezing point depression
Clinical Applications
- • Evaluation of dehydration/hydration status
- • Assessment of renal function
- • Diagnosis of SIADH (Syndrome of Inappropriate ADH)
- • Monitoring diabetes insipidus
- • Toxic alcohol ingestion detection
- • Critical care fluid management
Important Note
Osmolality vs Osmolarity: Osmolality (mOsm/kg H₂O) is measured per kg of solvent, while osmolarity (mOsm/L) is measured per liter of solution. For dilute aqueous solutions, they are numerically similar (~1-3% difference).
Osmolality Reference Values
| Fluid Type | Normal Range (mOsm/kg) | Clinical Significance | Common Causes of Abnormalities | Typical Use |
|---|---|---|---|---|
| Serum/Plasma | 275-295 | Fluid balance, renal function | Dehydration, diabetes, renal failure | Routine clinical assessment |
| Urine | 50-1200 | Renal concentrating ability | DI, SIADH, renal tubular disorders | Water deprivation test |
| Cerebrospinal Fluid | 290-305 | Blood-brain barrier integrity | Meningitis, CNS disorders | Neurological assessment |
| Ascitic Fluid | Similar to serum | Portal hypertension assessment | Liver cirrhosis, heart failure | Ascites evaluation |
| Saliva | 50-100 | Salivary gland function | Sjögren's syndrome, dehydration | Dry mouth assessment |