Avogadro's Number Calculator

Required if calculating moles from mass.
Chemistry

The Avogadro's Number Calculator converts between moles, number of particles, and mass using Avogadro's constant (6.022 × 10²³ particles per mole). Pick a mode, enter your value, and it returns the matching quantity — moles from particles, particles from moles, or both from a mass in grams. It's the everyday tool for stoichiometry and counting atoms or molecules.

Formula

n = N ÷ Nₐ and N = n × Nₐ, where Nₐ = 6.022 × 10²³ mol⁻¹
  • Avogadro's number (Nₐ = 6.022 × 10²³ per mole) is the count of particles — atoms, molecules, or ions — in exactly one mole of a substance.
  • Moles from particles: n = N ÷ Nₐ. Particles from moles: N = n × Nₐ.
  • Mass mode first finds moles with n = mass ÷ molar mass, then particles with N = n × Nₐ.
  • Input definitions: • Input value: moles, particles, or grams depending on the mode you choose. • Molar mass: the substance's mass per mole in g/mol, needed only for mass mode.
  • Use grams and g/mol consistently; the molar mass comes from the periodic table or a compound's formula.
  • The calculator uses the exact CODATA value 6.02214076 × 10²³ mol⁻¹, which is the modern definition of the mole.

Example Calculation

Inputs
  • Calculate: mass
  • Input value: 18.015
  • Molar mass (g/mol) - for mass mode: 18.015

In mass mode, 18.015 g of water (molar mass 18.015 g/mol) is 18.015 ÷ 18.015 = 1 mole. That mole contains 1 × 6.022 × 10²³ ≈ 6.022 × 10²³ water molecules.

Frequently asked questions

What is Avogadro's number?
Avogadro's number is 6.022 × 10²³, the number of particles (atoms, molecules, or ions) in one mole of any substance.
How do I convert moles to particles?
Multiply the number of moles by Avogadro's number: particles = moles × 6.022 × 10²³.
How do I convert particles to moles?
Divide the number of particles by Avogadro's number: moles = particles ÷ 6.022 × 10²³.
How do I get particles from a mass in grams?
First convert mass to moles using the molar mass (moles = grams ÷ g/mol), then multiply by Avogadro's number to get particles.
What is a mole?
A mole is a counting unit in chemistry equal to 6.022 × 10²³ particles, just as a dozen means 12. It links the atomic scale to measurable masses.
Where do I find the molar mass?
Add up the atomic masses (from the periodic table) of every atom in the substance's formula. For water (H₂O) that's about 18.015 g/mol.