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 loads instantly in the page, so you'll see the moles update as you type, and nothing you type is uploaded.

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.

It depends on whether you mean a gas or a solution. For an ideal gas at standard temperature and pressure, moles equals the volume in liters divided by 22.4, so 11.2 liters is 0.5 mole and you don't even need the molar mass. For a solution, moles equals the molarity times the volume in liters, so 0.5 molar across 2 liters is 1 mole. Pick the solution mode here for the second case, and use the 22.4 rule or our ideal gas law tool for the first.

Divide the number of molecules by Avogadro's number, since that's how many particles sit in one mole. So 1.2044 times 10 to the 24th molecules works out to 2 moles. This calculator does the reverse for you as well, showing the particle count next to the moles, so you can read the count that matches any mass or solution you enter.

Convert the milliliters to liters first by dividing by 1000, then use the solution route. So 500 milliliters is 0.5 liter, and at 2 molar that's 1 mole. Enter the volume in liters in the solution mode above, and it multiplies by the molarity for you. Milliliters on their own don't give moles, since you still need the concentration or a molar mass to tie volume to amount.

Yes, it's completely free, with no sign-up, and it runs right in your browser, so nothing you type is uploaded. 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.