Molar mass
Mass of substance
Volume of solution

Molarity Calculator


This molarity calculator is a tool for converting the mass concentration of any solution to molar concentration (or, otherwise speaking, recalculating grams per ml to moles). You can also calculate what is the required mass of the substance to achieve a desired molarity. This article will provide you with the definition and formula for molarity, as well as with a short step-by-step tutorial of how to calculate molarity of a concentrated solution.

What is molarity?

Molarity is the measure of concentration of a solution, expressed as the number of moles of solute (substance) per a liter of solution. The unit molar (symbol: M) is equivalent to 1 mole of substance in a liter of solution.

What is a mole, then? It is defined as the amount of a substance that contains as many particles (such as molecules or ions) as there are atoms is 12 grams of carbon-12. This number is equal to Avogadro constant: 6.022 * 10^23.

Molarity has many applications. One of them is the calculating the solution dilution.

Molarity formula

The following equation will allow you to find the molarity of a solution:

molarity = concentration / molar mass

The concentration denotes mass concentration of the solution, expressed in the units of density. It tells you what mass of the substance is present in a given volume of the solution. The most common units used are g/ml or g/l. Remember that 1 liter is equal to 1 cubic decimeter.

Molar mass is the mass of 1 mole of the solute. It is expressed in grams per mole. It is a constant property of each substance - for example, the molar mass of water is approximately equal to 18 g/mol.

Our calculator can also find the mass of substance you need to add to your solution to obtain a desired molar concentration, according to the formula

mass / volume = concentration = molarity * molar mass

where mass is the mass of solute (substance) in grams, and volume is the total volume of the solution in liters.

How to calculate molarity

  1. Choose your substance. Let's assume that it is the hydrochloric acid (HCl).
  2. Find the molar mass of your substance. For the hydrochloric acid it is equal to 36.46 g/mol.
  3. Decide on the mass concentration of your substance - you can either input it directly or fill put the boxes for substance mass and solution volume. Let's assume that you have 5 g of HCl in a 1.2 liter solution.
  4. Convert the expressions above to obtain a molarity formula. As mass / volume = molarity * molar mass, then mass / (volume * molar mass) = molarity.
  5. Substitute the known values to calculate the molarity: molarity = 5 / (1.2 * 36.46) = 0.114 mol/l = 0.114 M.
  6. You can also use this molarity calculator to find the mass concentration or molar mass. Simply type in the remaining values and watch it do all work for you.
Bogna Haponiuk

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