Moles Calculator

You pick what you have, then enter the values. From a mass it divides the grams by the molar mass to get moles. From a solution it multiplies the molarity by the volume in liters. It can also go the other way, turning moles back into grams. It then shows the number of particles too. Everything runs in your browser, so you'll see the moles update as you type, and nothing you enter leaves your device.

The usual route is moles equals mass divided by molar mass. You weigh the substance in grams, look up its molar mass in grams per mole, then divide. So 18 grams of water, with a molar mass of 18.02, is about 1 mole. If you have a solution instead, moles equals the molarity times the volume in liters, so 0.5 molar across 2 liters is also 1 mole. The calculator runs whichever route fits what you know.

A mole is just a counting unit for atoms and molecules, like a dozen is for eggs, except it's a huge number: 6.022 times 10 to the 23rd, called Avogadro's number. Chemists use it because atoms are far too small and numerous to count one by one. One mole of any substance contains that many particles, and it weighs the substance's molar mass in grams, which ties grams, moles, and particle counts neatly together.

Multiply the moles by the molar mass. Since moles equals grams over molar mass, flipping it gives grams equals moles times molar mass. So 2 moles of water at 18.02 grams per mole weighs 36.04 grams. Switch this tool to the grams mode, enter the moles and the molar mass, and it does that multiplication for you. It's the step you need whenever a recipe or reaction is written in moles but you're measuring on a scale.

Avogadro's number is 6.022 times 10 to the 23rd, the count of particles in one mole. It's enormous because atoms are tiny, so even a teaspoon of water holds a staggering number of molecules. To turn moles into a particle count you multiply by this number, and to go back you divide. This tool shows the particle count alongside the moles, so you can see just how many atoms or molecules your sample really contains.

Yes, it's completely free, with no sign-up, and it runs right in your browser, so nothing you enter leaves your device. Choose your starting point, type the values, and read the moles, grams, or particle count in a tap. Bookmark it for stoichiometry, lab prep, or chemistry homework, and pair it with the molar mass tool, which gives you exactly the number this one needs to turn grams into moles.