Osmolarity Calculator
Determine the osmotic concentration (osmoles of solute particles per liter of solution) and evaluate solution tonicity relative to standard physiological ranges.
Solute Properties
Input concentration values and ionization properties.
* Represents how many particles a solute splits into in solution (e.g. Glucose = 1, NaCl = 2, MgCl₂ = 3).
Calculated Osmolarity
* Tonicity status: Isotonic (vs blood plasma).
Physiological Range
Human blood plasma has an osmolarity of 280–300 mOsm/L. Hypotonic solutions (<280) cause cell swelling; hypertonic (>300) cause shrinking.
Biological Fluids & Saline Solutions Osmolarity Reference Table
| Fluid / Laboratory Saline | Osmolarity (mOsm/L) | Toxicity / Tonicity Classification | Key Solute Components |
|---|---|---|---|
| Normal Saline (0.9% NaCl) | 308 mOsm/L | Isotonic | 154 mM NaCl (i = 2) |
| Human Blood Plasma | 285–295 mOsm/L | Isotonic Standard | Na+, Cl-, HCO3-, Glucose, Proteins |
| D5W (5% Dextrose in Water) | 252 mOsm/L | Slightly Hypotonic | 252 mM Glucose (i = 1) |
| 3% Hypertonic Saline | 1,026 mOsm/L | Hypertonic | 513 mM NaCl (i = 2) |
Methodology & Equations
Osmolarity Formula
Multiplies chemical concentration ($M$) by the van 't Hoff dissociation factor ($i$).
Tonicity Assessment
Compares calculated mOsm/L against human plasma standard (280–300 mOsm/L).
Frequently Asked Questions
What is Osmolarity? ▼
Osmolarity (Osm/L or mOsm/L) is the measure of solute particle concentration per liter of solution. It accounts for solute ionization/dissociation in solvent.
What is the van 't Hoff factor (i)? ▼
The van 't Hoff factor ($i$) represents the number of distinct particles a solute molecule forms when dissolved. Non-electrolytes like glucose have $i = 1$, NaCl dissociates into $^+$ and $^-$ ($i = 2$), and $_2$ dissociates into $^{2+}$ and $2^-$ ($i = 3$).
Why is osmolarity important in cell culture and blood plasma? ▼
Mammalian cells require isotonic media (~290 mOsm/L). Hypotonic solutions cause cell lysis due to water influx, while hypertonic solutions cause cell crenation due to osmotic water loss.
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