Molarity Calculator

Determine the mass, concentration, or volume required to make a solution.

Click on the tab for the value you’d like to calculate (Mass, Concentration, or Volume). Enter your three known values and click the Calculate button. Your missing value will appear in the box to the left. Click the Clear button to clear all fields.

Guidelines and examples for calculating molarity

The molarity calculator is based on the following equation:

Mass (g) = Concentration (mol/L) × Volume (L) × Molecular Weight (g/mol)

Examples of Using This Calculator:

Assume you are preparing a stock solution of prostaglandin E2 (PGE2) in DMSO. The molecular weight of PGE2 is 352.5 g/mol.

To calculate Mass: If you need to calculate the mass of PGE2 required to reach a final concentration of 10 mM and volume of 250 µl:

Click the Mass tab

Enter 10 into the Concentration field and select the correct unit (millimolar)

Enter 250 into the Volume field and select the correct unit (microliters)

Enter 352.5 into the Molecular Weight field

Press calculate - The answer of 881.25 micrograms appears in the Mass box

To calculate Concentration: If you have 1 mg of PGE2 and a final volume of 250 µl you can do the following steps to calculate the molar concentration of your solution:

Click the Concentration tab

Enter 1 into the Mass field and select the correct unit (milligrams)

Enter 250 into the Volume field and select the correct unit (microliters)

Enter 352.5 into the Molecular Weight field

Press calculate - The answer of 11.3475 millimolar appears in the Concentration box

To calculate Volume: If you have 1 mg of PGE2 and are trying to work out the volume of solution required to reach a concentration of 10 mM:

Click the Volume tab

Enter 1 into the Mass field and select the correct unit (milligrams)

Enter 10 into the Concentration field and select the correct unit (millimolar)

Enter 352.5 into the Molecular Weight field

Press calculate - The answer of 283.6879 microliters appears in the Volume box

Additional Tips:

Click the Clear button to clear all fields.

You can hit the Enter key on your keyboard instead of clicking the Calculate button.

If you don’t have a known molecular weight for your compound, you can easily calculate it by using ourMolar Mass Calculator.

Mass

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grams/mole

Concentration

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grams/mole

Volume

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grams/mole