Calculate molarity, moles, or solution volume from any two values using mol, mmol, μmol, L, mL, and M, mM, or μM units in chemistry.
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Molarity Formula
The molarity calculator uses the relationship between moles of solute, liters of solution, and molarity.
- M = molarity, in moles per liter, usually written as M or mol/L
- n = moles of solute, in mol
- V = volume of solution, in liters
To calculate molarity, enter moles of solute and volume of solution. The calculator divides moles by liters.
To calculate moles, enter molarity and volume. The calculator multiplies molarity by liters.
To calculate volume, enter moles and molarity. The calculator divides moles by molarity.
If you use mmol, μmol, mL, mM, or μM, the values are converted to base units first. Moles are converted to mol, volume is converted to L, and molarity is converted to M before the formula is applied.
Molarity Units and Conversions
Use these conversions to check that your inputs use the correct scale.
| Quantity | Unit | Base-unit conversion |
|---|---|---|
| Amount of solute | 1 mol | 1 mol |
| Amount of solute | 1 mmol | 0.001 mol |
| Amount of solute | 1 μmol | 0.000001 mol |
| Volume | 1 L | 1 L |
| Volume | 1 mL | 0.001 L |
| Molarity unit | Equivalent in M | Equivalent description |
|---|---|---|
| 1 M | 1 M | 1 mole per liter |
| 1 mM | 0.001 M | 1 millimole per liter |
| 1 μM | 0.000001 M | 1 micromole per liter |
Example Problems
Example 1: Calculate molarity
You dissolve 0.50 mol of solute in enough solution to make 2.00 L. Find the molarity.
The molarity is 0.25 M.
Example 2: Calculate moles
You have 250 mL of a 0.200 M solution. Find the moles of solute.
First convert 250 mL to liters:
Then multiply molarity by volume:
The amount of solute is 0.0500 mol, or 50.0 mmol.
FAQ
What does molarity mean?
Molarity is the number of moles of solute per liter of solution. A 1 M solution contains 1 mole of solute in each liter of solution.
Is volume the amount of solvent or the total solution?
Use the total final volume of the solution. For example, if you dissolve a solid in water and then dilute the mixture to 500 mL, the volume is 500 mL. It is not just the amount of water you started with.
Why does the calculator require exactly two values?
The molarity equation has three variables: molarity, moles, and volume. If you enter any two, the third can be calculated. If you enter fewer than two values, there is not enough information. If you enter all three, there is no missing value to solve for.
