Why does NaCl use i = 2?

NaCl fully dissociates in water into one Na⁺ ion and one Cl⁻ ion, so each dissolved formula unit produces two separate osmotically active particles.

What about substances that don't dissociate, like glucose?

For non-ionic solutes like glucose that stay as one intact molecule in solution, use i = 1, so osmolarity equals the molarity directly.

Osmolarity Calculator

Calculate osmolarity — the total concentration of dissolved particles in a solution — from the solute's molarity and the number of particles (ions) it dissociates into. Important in physiology, IV fluid preparation, and lab science.

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Results

Osmolarity: 1 Osm/L

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Formula

Osmolarity = Molarity × Number of Particles Per Molecule (i)

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