Molarity Calculator

You choose how you're starting, from a mass of solute or from moles, then enter the values and the solution volume. From a mass it finds the moles by dividing by the molar mass, then divides those moles by the volume in liters for the molarity. Everything runs in your browser, so you'll see the concentration update as you type, and nothing you enter leaves your device. It also shows the moles and the grams-per-liter alongside.

Molarity is moles of solute divided by liters of solution. If you have a mass, first turn it into moles by dividing the grams by the molar mass, then divide by the volume. So 58.44 grams of table salt, which has a molar mass of 58.44, is exactly 1 mole, and dissolved in 1 liter that's a molarity of 1, written 1 M. The calculator runs both steps the moment you type the mass, molar mass, and volume.

Molarity is the most common way to express concentration in chemistry: the number of moles of a dissolved substance per liter of solution. A 2 M solution has 2 moles in every liter. It's written with a capital M, so 0.5 M reads as half-molar. Because reactions happen mole for mole, molarity lets you measure out exact amounts for a reaction, which is why it shows up all over lab work and homework.

They sound alike but divide by different things. Molarity is moles per liter of solution, while molality is moles per kilogram of solvent. Molarity is easier to measure, since you just make up a volume, so it's the everyday choice. Molality matters when temperature changes, because volume shifts with heat but mass doesn't, so it's used for boiling-point and freezing-point work. This tool calculates molarity, the one you'll meet most often.

Add up the atomic masses of every atom in the formula. For table salt, NaCl, sodium is about 22.99 and chlorine about 35.45, so the molar mass is 58.44 grams per mole. For water, two hydrogens at 1.008 plus one oxygen at 16.00 gives 18.02. Once you have that number, type it into the molar mass box here. The reference table below lists a few common compounds to get you started.

Yes, it's completely free, with no sign-up, and it runs right in your browser, so nothing you enter leaves your device. Pick your starting point, type the mass or moles and the volume, and read the molarity in a tap. Bookmark it for chemistry class, lab prep, or making up solutions, and you'll have the molarity formula, the moles, and the concentration all in one place whenever you need them.