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Molarity CalculatorFree online other calculator — instant results, no sign-up

Molarity from mass, molar mass and volume.

Inputs

g
g/mol
L
Moles
0.1001
Molarity1.00103 M

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About the Molarity Calculator

The Molarity Calculator determines the chemical concentration of a solution based on the mass of solute dissolved, its molar mass, and the total volume of the solution. It is commonly used by students, researchers, and laboratory technicians preparing chemical reagents and standard solutions. The tool outputs both the total moles of solute and the resulting molarity in moles per liter.

Solute mass
The measured mass of the pure dissolved substance in grams (g), greater than 0.
Molar mass
The mass of one mole of the chemical compound in grams per mole (g/mol), greater than 0.
Solution volume
The final total volume of the liquid solution in liters (L), greater than 0.

Formula and method

Moles = Solute mass / Molar mass
Molarity = Moles / Solution volume = Solute mass / (Molar mass × Solution volume)
  • MolesAmount of solute substance in moles (mol)
  • MolarityMolar concentration of the solution in moles per liter (M or mol/L)
  • Solute massMass of the dissolved solute in grams (g)
  • Molar massMolecular or formula weight of the solute in grams per mole (g/mol)
  • Solution volumeTotal final volume of the prepared solution in liters (L)

The calculator first divides solute mass by molar mass to determine the number of moles. It then divides that mole count by the total solution volume in liters to obtain molarity. Both the mole count and molarity values are rounded to 5 decimal places.

Worked example

These are the calculator's starting values and the results it actually produces for them.

Inputs

  • Solute mass5.85 g
  • Molar mass58.44 g/mol
  • Solution volume0.1 L

Results

  • Moles0.1001
  • Molarity1.00103 M

How to use the Molarity Calculator

  1. 1Divide the solute mass in grams by the compound's molar mass in grams per mole to calculate total moles.
  2. 2Verify the final solution volume is expressed in liters.
  3. 3Divide the calculated moles by the solution volume in liters.
  4. 4Format the resulting molar concentration with the molarity unit symbol (M).

Reading your result

The 'Moles' output shows the absolute quantity of solute molecules present in the mixture. 'Molarity' reflects the concentration, where 1 M represents one mole of solute per liter of final solution. Higher molarity values indicate a more concentrated solution, whereas smaller values represent a dilute solution.

Limitations

The calculation relies on final solution volume, not solvent volume added, and does not account for volume contraction or expansion during dissolution. It also assumes 100% solute purity and does not adjust for temperature changes, which affect liquid density and volumetric measurements.

Common questions

What is the difference between molarity and molality?+

Molarity (M) measures moles of solute per liter of total solution volume, which varies slightly with temperature. Molality (m) measures moles of solute per kilogram of solvent mass, which remains constant across temperature changes.

Should I add the specified volume of water directly to the solute?+

No. Dissolving a solid solute into an exact volume of water often causes the final volume to exceed that amount. In laboratory practice, dissolve the solute in a smaller amount of solvent first, then dilute to the target volume mark in a volumetric flask.

How do I convert milliliters to liters for this calculation?+

Divide the volume in milliliters (mL) by 1,000 to convert to liters (L). For example, 250 mL equals 0.25 L.

Does the calculator save my information?+

Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.

Further reading

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Results are estimates for informational purposes and are not financial, medical or legal advice.