Measure osmolarity quickly from ions, sugars, and dilution data. Compare ideal and adjusted concentration outputs. Create cleaner lab calculations with exports, examples, and guidance.
Use mol/L, mmol/L, or g/L inputs. For g/L, provide molar mass. Measured mode applies the osmotic coefficient to each row.
Core relation: Osmolarity = Σ(C × i × φ)
Here, C is molarity in mol/L, i is the van’t Hoff particle factor, and φ is the osmotic coefficient. The calculator multiplies the summed value by 1000 to report mOsm/L.
Unit conversion: mmol/L ÷ 1000 = mol/L. For g/L inputs, molarity = concentration ÷ molar mass.
Batch osmoles: total mOsm in the prepared batch = osmolarity × final volume in liters.
Approximate osmotic pressure: π ≈ Osmolarity × R × T, using total osmoles per liter, the gas constant, and absolute temperature.
| Solute | Concentration | Unit | Molar Mass | Particles | Phi | Estimated Contribution |
|---|---|---|---|---|---|---|
| Sodium Chloride | 154 | mmol/L | 58.44 | 2 | 0.93 | 286.44 mOsm/L |
| Glucose | 5 | mmol/L | 180.16 | 1 | 1.00 | 5.00 mOsm/L |
| Mannitol | 27.3 | g/L | 182.17 | 1 | 1.00 | 149.86 mOsm/L |
Osmolarity measures the total number of osmotically active particles per liter of solution. It helps compare how strongly different mixtures attract water across a semipermeable membrane.
Particle count reflects dissociation. Sodium chloride yields roughly two particles, while glucose stays as one. More particles increase osmolarity even when molar concentration stays unchanged.
Use the osmotic coefficient when real solutions deviate from ideal behavior. Electrolytes, concentrated mixtures, and practical formulations often require this correction for better estimates.
Yes. The calculator converts g/L to mol/L by dividing by molar mass. This option is useful when formulation sheets list masses rather than molar concentrations.
No. Osmolarity is based on solution volume, while osmolality uses solvent mass. They can be close in dilute aqueous systems but differ more in concentrated mixtures.
A result near 275 to 295 mOsm/L is often treated as near isotonic. The exact acceptable range depends on the application, formulation goals, and biological system.
No. They are quick theoretical estimates based on standard relations. Real systems can differ because of nonideality, temperature dependence, specific interactions, and experimental conditions.
You can export the displayed calculation summary and contribution table as a CSV or PDF file. Exports make documentation easier for reports, teaching notes, and lab records.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.