Osmolarity converter
Convert molarity to osmolarity and back. Pick the solute: salt splits into two particles, so 150 mM saline is 300 mOsm/L.
That's about the same as a hypotonic solution. That is hypotonic: cells placed in it would swell.
What it means
How concentrated is that?
Real salts do not dissociate perfectly, so measured osmolarity runs a few percent below the ideal figure. The osmotic coefficient of saline is about 0.93.
Every unit
Your osmolarity in every unit
Learn
Three things worth knowing
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mOsm/L = mmol/L × particles
150 mM sodium chloride is 300 mOsm/L, because each unit splits into a sodium and a chloride.
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Osmolarity or osmolality
Osmolarity is per liter of solution, osmolality per kilogram of water. In dilute body fluids they barely differ, which is why laboratories use them almost interchangeably.
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Percent is not concentration
5% glucose and 0.9% saline are both "isotonic", but the glucose is 278 mOsm/L and the saline 308. The percentages are by weight, and the molecules are different sizes.
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Background
About osmolarity
Osmosis counts particles, not molecules. A mole of glucose gives one mole of particles; a mole of sodium chloride gives two; calcium chloride gives three.
Plasma sits at about 290 mOsm/L, which is why 0.9% saline — 154 mM, so 308 mOsm/L — is the fluid you can put into a vein.