What Is the Concentration Calculator?
This concentration calculator finds the molarity of a solution — the amount of dissolved substance (solute) per liter of solution. Molarity, symbolized M, is one of the most common ways chemists express concentration and is essential for preparing reagents, performing dilutions, and running titrations.
How to Use It
Enter the number of moles of solute and the total volume of the solution in liters. The calculator divides moles by volume to return the concentration in mol/L (M), and also shows the equivalent value in millimolar (mM). If you know mass instead of moles, first divide the mass (g) by the molar mass (g/mol) to get moles.
The Formula Explained
The core equation is:
$$M = \frac{\text{Moles (mol)}}{\text{Volume (L)}}$$
Note that the volume is the total volume of the solution, not just the solvent you started with. One molar (\(1\,M\)) means one mole of solute is dissolved in enough solvent to make one liter of solution.
Worked Example
Suppose you dissolve 0.5 moles of sodium chloride in enough water to make 2 liters of solution. Molarity = $$0.5 \div 2 = 0.25\ M$$, which is the same as 250 mM. So the solution is 0.25 molar.
FAQ
What is the difference between molarity and molality? Molarity (M) uses liters of solution, while molality (m) uses kilograms of solvent. Molarity changes slightly with temperature because volume expands; molality does not.
How do I convert grams to moles? Divide the mass in grams by the molar mass of the compound (g/mol). For example, 58.44 g of NaCl is 1 mole.
What if my volume is in milliliters? Divide the volume in mL by 1000 to convert it to liters before entering it here.
