How molarity works
Molarity expresses concentration as the number of moles of dissolved substance per litre of solution, written M = moles ÷ litres. It is the most common way chemists describe how strong a solution is.
Choose which of the three quantities you want, and the calculator rearranges the same relationship to solve for it: molarity from moles and volume, moles from molarity and volume, or volume from moles and molarity.
Using the result
Molarity tells you how much solute sits in each litre, which lets you scale a recipe up or down or work out how much to weigh out for a target concentration.
- Solve for moles to find how much solute a given volume contains.
- Solve for volume to find how much solution a fixed amount of solute makes.
Practical tips
Molarity is based on the volume of the finished solution, not the volume of solvent you started with, because dissolving a solid can change the total volume.
- Convert millilitres to litres before entering volume.
- Convert a mass of solute to moles using its molar mass first.
Caveats and common mistakes
Volume must be greater than zero when solving for molarity, and molarity must be positive when solving for volume, since both involve dividing by that value. Molarity also shifts slightly with temperature because liquid volume expands and contracts.
Formula
M = moles / litres