Avogadro's Number Calculator
Convert between moles, number of particles, and grams using Avogadro's number and molar mass.
One mole is 6.022 × 10²³ particles — atoms, molecules, ions, whatever you're counting. Enter an amount in any of the three units and the calculator converts to the others. Grams need a molar mass; you can look it up with the molar mass calculator.
Moles
2mol
Particles
1.204e+24
Mass
36.03g
How it works
Avogadro's number, 6.022 × 10²³, is the count of particles in one mole. It's a chemist's dozen — a bulk unit for atoms, molecules, or ions, which are far too small to count one by one. Say 'a mole of water' and you mean 6.022 × 10²³ water molecules.
Converting moles to particles is a single multiplication, and going back is a division. This calculator handles both directions: enter an amount in moles, particles, or grams and it fills in the other two. Pick what you're starting from with the toggle so it knows which way to run the conversion.
The grams column needs one extra piece of information — the molar mass, in grams per mole. That's the bridge between the count of particles and their actual weight. Water is about 18.015 g/mol, so a mole of it weighs roughly 18 grams. If you don't know a substance's molar mass, the molar mass calculator will work it out from the formula.
Frequently asked questions
What exactly does Avogadro's number count?
It counts whatever elementary units you specify — atoms, molecules, ions, or electrons. One mole of anything contains 6.022 × 10²³ of those units. The number itself is just a fixed count; the substance decides what's being counted.
Why do I need the molar mass for grams?
Moles and particles are about how many; grams are about how heavy. Molar mass links the two by telling you the mass of one mole. Without it, the calculator can convert between moles and particles but can't reach a weight in grams.
How do I find a substance's molar mass?
Add up the atomic weights of every atom in its chemical formula. Water, H₂O, is roughly 2 × 1.008 plus 15.999, about 18.015 g/mol. The molar mass calculator does this automatically once you type in the formula.