Molarity Calculator: Calculate Molar Concentration, Mass, and Volume

In chemistry, we do calculate solution concentrations, and Molarity (M) is the standard measurement. To make this quick, easy, and accurate, we have added the Molarity Calculator tool to our chemical engineering calculator list.

Before we get into the tools, let’s have a quick introduction to the definition and formula.

What is Molarity?

Molarity, also known as molar concentration, is a measure of the concentration of a solute in a solution, in terms of the amount of substance per unit volume of solution.

It is how many moles of a specific substance are dissolved in exactly one liter of liquid. Molarity unit is mol/L and is denoted by M.

Where:

• M = Molarity (mol/L)
• n = Number of moles of solute (mol)
• V = Volume of solution in liters (L)

   

If the mass concentration of the substance is know, then substituting the value of n, we have equation below.

   

How to Use the Molarity Calculator

1. Enter the molecular weight (molar mass) of the solute — this is required for calculating molarity.
2. Choose one of the two methods to calculate molarity:
   • Method 1: Using mass concentration
     Enter the mass concentration (g/L, g/mL, mg/mL, etc.) to get molarity directly.
   • Method 2: Using mass and volume of solution
     Enter the solute mass and solution volume to calculate mass concentration and then molarity.
3. Click Calculate Molarity to see the molar concentration (mol/L).
4. If you used the mass + volume method, the tool also displays mass concentration in g/L.

Example

A solution contains 12 mg/mL of a solute whose molar mass is 150 g/mol. Calculate the molarity (mol/L) of the solution.

Step 1: Convert mg/mL to g/L

12 mg/mL=12 g/L

Step 2: Apply the molarity formula$$M = \frac{\text{mass concentration (g/L)}}{\text{molar mass (g/mol)}}$$Step 3: Substitute values$$M = \frac{12}{150} = 0.08\ \text{mol/L}$$

The molarity of the solution is 0.08 M.