Molarity Calculator
Molarity ties moles of solute to liters of solution with M = mol/L. Enter any two and it fills in the third, and it'll turn grams into moles for you too.
Molarity is moles of solute divided by liters of solution, M = mol/L. Fill in any two of moles, volume, and molarity and leave the third blank — it solves for the empty one. Dissolve 0.5 mol of salt in 2 L and you're at 0.25 M.
Optional: don't know the moles? Enter grams and molar mass.
Molarity
0.25mol/L
Moles
0.5mol
Volume
2L
How it works
Molarity measures how crowded a solution is: moles of solute divided by liters of solution, written M = mol/L. Drop 0.5 mol of table salt into 2 L of water and you're sitting at 0.25 M.
Fill in any two of moles, volume, and molarity, and leave the one you're after blank. The tool rearranges the formula — moles is molarity times volume, volume is moles over molarity — and quietly skips any division by zero instead of printing nonsense.
Working from a mass instead? Type the grams and the molar mass into the optional box and it converts to moles first (grams over molar mass), then feeds that straight into the molarity math above.
Frequently asked questions
What's the difference between molarity and moles?
Moles count how much substance you have, full stop. Molarity tells you how concentrated it is once dissolved — the same moles in a smaller volume give a higher molarity.
How do I get moles from grams?
Divide the mass in grams by the molar mass in g/mol. The calculator does this automatically if you fill in the optional grams and molar-mass fields, then uses the result as the moles.
Does the volume have to be in liters?
Molarity is defined per liter, so convert first. A 250 mL solution is 0.25 L. Enter volumes in liters and the molarity comes out in the standard mol/L.