HesapHanem

Molarity Calculator

Find the molarity of a solution.

How it is calculated

Molarity is the concentration of a solution: M = n ÷ V, where n is the amount of dissolved substance (solute) in moles and V is the volume of the whole solution in litres. The answer is in mol/L, written as M, shown with three decimals. Volume must be above zero. If you only know the mass of solute, first divide by the molar mass (g/mol) to obtain moles. Molarity depends on temperature slightly, because the volume of a liquid changes as it warms; the formula itself ignores that.

Worked example

You dissolve 0.5 mol of a salt and make the solution up to 2 litres. Molarity = 0.5 ÷ 2 = 0.25. The tool shows 0.250 mol/L. If you took 100 mL (0.1 L) of it, that portion would hold 0.025 mol, because concentration stays the same however much you pour out.

Try this example →

Common mistakes

  • Using the volume of solvent instead of the final solution. The litres should be the total volume after dissolving.
  • Entering millilitres. 250 mL must be typed as 0.25 L, otherwise the molarity is 1,000 times too small.
  • Entering grams where moles are expected. Divide the mass by the molar mass first.
  • Confusing molarity with molality. Molality is moles per kilogram of solvent, which is a different number.
  • Forgetting dilution. Adding water to a solution lowers the molarity, because the same moles are spread over a larger volume.

About this calculator

This calculator finds molarity, M = moles of solute ÷ liters of solution, the standard unit chemists use to express how concentrated a solution is.

Chemistry students use it constantly in lab reports and titration calculations, and lab technicians use it to prepare reagents at an exact concentration — get the molarity wrong and an experiment's results become meaningless. The tool takes the moles and the volume in litres and returns the molarity; if you start from a mass, first divide it by the molar mass to get moles.

Was this helpful?

You can pick up to 3 reactions.

Comments (1)

  • Editorial team

    To prepare a solution, work backwards: moles needed are the target molarity times the final volume, and the mass to weigh is moles times molar mass. For 500 mL of 0.1 M NaCl that is 0.05 mol, or about 2.92 g, which you can confirm by entering 0.05 and 0.5 here. Dissolve it, then top up to the mark. This tool takes moles, not grams. Which solution are you making?

Popular calculators

Loan Calculator

Monthly payment, total interest and full amortization schedule.

Percentage Calculator

Percent change, percent of, and ratio calculations.

Discount Calculator

Calculate final price, savings, and discount amount.

BMI Calculator

Body mass index from height and weight (metric or imperial).

Age Calculator

Compute your exact age in years, months and days from a birth date.

Compound Interest Calculator

Calculate the final amount and interest earned with compounding.

All Calculators