Atoms to Moles Calculator
Convert a number of atoms, molecules or ions to moles and back using the Avogadro constant, 6.022 × 10²³ per mole.
How many particles are in a mole, and the other way round.
How the atoms to moles calculator works
One mole contains exactly 6.02214076 × 10²³ particles — the Avogadro constant. Moles = particles ÷ N_A; particles = moles × N_A. Enter large numbers in scientific notation (3.5e24) — the calculator understands it.
Formula: n = N ÷ N_A · N = n × N_A (N_A = 6.02214076 × 10²³ mol⁻¹)
Worked examples
| Inputs | Result | Note |
|---|---|---|
| 3.011 × 10²³ atoms → moles | 0.499988 | 0.5 mol |
| 2 moles → molecules | 1.2044e24 | 1.204 × 10²⁴ |
| 1 × 10²⁰ ions → moles | 0.000166 | 0.000166 mol |
FAQFrequently asked questions
Why is Avogadro's number so large?
Because atoms are so small: it is the number of carbon-12 atoms in 12 g. Since 2019 it is defined exactly as 6.02214076 × 10²³.
Atoms or molecules — does it matter?
The count is of whatever particle you name: a mole of water is 6.022 × 10²³ molecules, containing three times as many atoms.
How do I type 10²³?
As 1e23. The calculator reads scientific notation in the input and shows it in the result.
How many atoms in a gram of gold?
1 ÷ 196.97 mol × 6.022 × 10²³ ≈ 3.06 × 10²¹ atoms.
Where these figures come from
- IUPAC — Standard atomic weights (2021 conventional values) — the molar-mass table
- NIST — CODATA 2018 fundamental physical constants — Avogadro constant, gas constant, speed of light
- NIST Chemistry WebBook — thermochemical data
- National Institute of Standards and Technology — the US measurement and reference-data authority
Last checked: September 2026. Atomic masses are the IUPAC conventional values; constants are CODATA 2018; equations are the standard textbook forms.