Convert between moles and the number of atoms or molecules using Avogadro's number (6.02214076 × 10²³ per mole). Enter a chemical formula to start from grams, get the molar mass and see how many atoms of each element are in your sample.
Last updated:
Convert
mol
g
Gives the molar mass and counts atoms of each element
g/mol
Leave empty to use the formula
Enter your values to see the result.
Advertisement
Advertisement
How to use the Moles to Atoms Calculator
Pick the conversion: moles to particles, particles to moles, grams to particles or particles to grams.
Enter your amount: moles, a particle count like 3.011e23, or grams.
Type the chemical formula (e.g. H2O) to get its molar mass and atom counts, or enter the molar mass yourself.
Read the result in scientific notation with the full working.
Check the element table for atoms of each element, or copy the results.
Avogadro's number formulas
Convert
Formula
Example
Moles → particles
N = n × NA
0.25 mol → 1.506 × 10²³
Particles → moles
n = N ÷ NA
1 × 10²⁴ → 1.661 mol
Grams → particles
N = (m ÷ M) × NA
18 g H₂O → 6.017 × 10²³ molecules
Particles → grams
m = (N ÷ NA) × M
1 × 10²³ CO₂ → 7.308 g
Atoms in a compound
atoms = molecules × atoms per molecule
1 mol CO₂ → 1.807 × 10²⁴ atoms
NA = 6.02214076 × 10²³ mol⁻¹ (exact), n = moles, m = mass in grams, M = molar mass in g/mol. To convert only between grams and moles, see the Grams to Moles Calculator.
Particles in one mole of common substances
Substance
Molar mass (g/mol)
Particles per mole
Atoms per mole
Carbon (C)
12.011
6.022 × 10²³ atoms
6.022 × 10²³
Iron (Fe)
55.845
6.022 × 10²³ atoms
6.022 × 10²³
Oxygen gas (O₂)
31.998
6.022 × 10²³ molecules
1.204 × 10²⁴
Water (H₂O)
18.015
6.022 × 10²³ molecules
1.807 × 10²⁴
Carbon dioxide (CO₂)
44.009
6.022 × 10²³ molecules
1.807 × 10²⁴
Sodium chloride (NaCl)
58.44
6.022 × 10²³ formula units
1.204 × 10²⁴ ions
Glucose (C₆H₁₂O₆)
180.156
6.022 × 10²³ molecules
1.445 × 10²⁵
Frequently asked questions
How do you convert moles to atoms?
Multiply the number of moles by Avogadro's number: atoms = moles × 6.02214076 × 10²³. For example, 2 mol of iron contains 2 × 6.022 × 10²³ = 1.204 × 10²⁴ atoms.
How do you convert atoms to moles?
Divide the number of atoms by Avogadro's number: moles = atoms ÷ 6.02214076 × 10²³. For example, 3.011 × 10²³ atoms ÷ 6.022 × 10²³ = 0.5 mol.
How many atoms are in a molecule-based sample?
First find the number of molecules (moles × Avogadro's number), then multiply by the number of atoms in one molecule. One mole of water (H₂O) has 6.022 × 10²³ molecules but 3 × 6.022 × 10²³ = 1.807 × 10²⁴ atoms: 1.204 × 10²⁴ hydrogen and 6.022 × 10²³ oxygen.
How do you convert grams to atoms?
Divide the mass by the molar mass to get moles, then multiply by Avogadro's number: atoms = (grams ÷ molar mass) × 6.022 × 10²³. For 12 g of carbon (12.011 g/mol) that is about 6.017 × 10²³ atoms.
What exactly is Avogadro's number?
Since the 2019 SI redefinition the Avogadro constant is fixed at exactly 6.02214076 × 10²³ per mole. One mole is the amount of substance that contains exactly that many specified particles (atoms, molecules, ions or electrons).
What is the difference between atoms and molecules here?
For a single element such as Fe or C the particles are atoms. For a compound such as CO₂ the particles are molecules (or formula units for ionic compounds like NaCl), and each one contains several atoms. The calculator shows both counts.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.