⚠️ Research Use Only. Not validated for clinical diagnostic use.
Osmolarity Calculator
Calculate osmolarity from solute composition for IV fluids, TPN, and buffer solutions. Enter solutes and get total mOsm/L.
Osmolarity from Solute Composition
Osmolarity = Σ(concentration × number of particles). For NaCl, particles = 2 (Na⁺ + Cl⁻). For glucose, particles = 1.
Results
Total Osmolarity
—mOsm/L
Number of Solutes
—
Isotonic? (~285-310)
—
Research use only — not for clinical fluid therapy. Osmolarity estimates are first-order; actual IV/TPN prescribing requires clinical assessment and institutional protocols.
Reference Values
| Solution | Composition | Osmolarity |
|---|---|---|
| Normal Saline (0.9% NaCl) | 154 mM NaCl | ≈308 mOsm/L |
| D5W (5% Dextrose) | 278 mM glucose | ≈278 mOsm/L |
| Lactated Ringer's | Multiple electrolytes | ≈273 mOsm/L |
| Plasma (reference) | — | ≈285-310 mOsm/L |
Frequently Asked Questions
What is osmolarity?
Osmolarity is the measure of solute concentration expressed as osmoles of solute per litre of solution (osmol/L or mOsm/L).
How is osmolarity calculated?
Osmolarity = Σ(concentration × number of particles). For non-electrolytes like glucose, particles = 1. For NaCl, particles = 2 (Na⁺ and Cl⁻).
What is the difference between osmolarity and osmolality?
Osmolarity is per litre of solution; osmolality is per kilogram of solvent. They are approximately equal for dilute aqueous solutions.
What is isotonic?
Isotonic solutions have approximately the same osmolarity as blood plasma (~285-310 mOsm/L).