Molarity Calculator

1. Enter any two of molarity, moles of solute and volume.
2. Use liters for the total solution volume.
3. Leave the one you want to find blank.
4. Read the result and the formula used.

Here is what each result means:

Molarity is the most common way chemists measure the concentration of a solution. It is the number of moles of dissolved solute per liter of solution, written with a capital M, so a 2 M solution contains 2 moles of solute in every liter. The more solute packed into each liter, the higher the molarity.

The key rule is simple: molarity equals moles divided by volume in liters. Because it is a ratio, the same molarity can come from a lot of solute in a lot of solution or a little in a little. A 0.25 molar solution could be 0.5 moles in 2 liters or 0.25 moles in 1 liter, since both give the same concentration.

One important detail is that the volume is the total volume of the finished solution, not the volume of water or other solvent you started with. Dissolving a solid adds a little to the volume, so chemists make up a solution to a fixed final volume in a flask. Using the solvent volume instead of the solution volume is a common source of error.

It rearranges one relation to solve for whichever value you leave blank.

1. For molarity, divide moles by volume in liters.
2. For moles, multiply molarity by volume.
3. For volume, divide moles by molarity.

Molarity connects amount and volume; see the ideal gas law calculator and proportion calculator for dilution ratios.

Dissolve 0.5 moles of solute to make 2 liters of solution.

Calculation: M = n / V = 0.5 / 2 = 0.25 molar. To find how many moles are in 0.5 liters of a 2 molar solution, multiply: 2 times 0.5 is 1 mole.

One relation, rearranged for whatever you need to find.

All three come from M equals n over V, so any two of the values give the third. This makes molarity easy to use when preparing a solution of a target concentration or working out how much solute a given volume contains.

Molarity is one of several ways to state concentration, each suited to a different purpose.

Molarity is the most convenient for lab work because volumes are easy to measure, but it changes slightly with temperature as the solution expands or contracts. Molality avoids this by using mass, so it is preferred for precise work over a range of temperatures.

The Amount of Solute

More moles of solute in the same volume gives a higher molarity, in direct proportion.

The Volume of Solution

A larger volume for the same amount of solute lowers the molarity. Diluting doubles the volume and halves the molarity.

The Temperature

Because volume changes slightly with temperature, molarity shifts a little when a solution is heated or cooled.

Chemistry Homework

Solve for molarity, moles or volume in a solution problem.

Preparing Solutions

Work out how much solute to dissolve for a target concentration.

Dilutions and Titrations

Find the moles present in a measured volume of a known solution.

1. Using Milliliters

Volume must be in liters. Divide milliliters by 1000 before entering them.

2. Solvent Instead of Solution

Use the total volume of the finished solution, not the volume of solvent you added.

3. Grams Instead of Moles

Molarity uses moles. Convert a mass in grams to moles using the molar mass first.

4. Confusing Molarity and Molality

Molarity uses volume of solution; molality uses mass of solvent. They are not the same.

5. Zero Volume or Molarity

Solving for molarity or volume cannot divide by zero.

The relation is exact; only the displayed decimals are rounded, and very large or small results are shown in scientific notation.

Molarity is the concentration of a solution measured as moles of solute per liter of solution, written M. A 2 M solution has 2 moles of solute in every liter.

Divide the moles of solute by the volume of solution in liters. Dissolving 0.5 moles to make 2 liters gives 0.5 divided by 2, which is 0.25 molar.

Multiply the molarity by the volume in liters. Leave the moles field blank and enter molarity and volume, and the calculator solves for it.

Molarity is moles per liter of solution, while molality is moles per kilogram of solvent. Molality does not change with temperature because it uses mass, not volume.

Use the total volume of the finished solution, not the volume of solvent added. Dissolving a solute changes the volume, so solutions are made up to a fixed final volume.

Divide the mass in grams by the molar mass of the substance in grams per mole. Then use that number of moles in the molarity formula.

Moles per liter, called molar and written M. Enter the amount in moles and the volume in liters. Convert milliliters to liters by dividing by 1000.

Slightly, because the volume of a solution expands when heated and contracts when cooled. For precise work over a temperature range, chemists often use molality instead.

No. The calculation runs in your browser and nothing you enter is stored or sent anywhere, unless you choose Save, which keeps the result only on this device.

• Molar concentration (Wikipedia).
• Molality (Wikipedia).
• Concentration (Maths Is Fun).