Mole Calculator (Grams, Moles, Particles)

Convert between grams, moles and number of particles with Avogadro’s constant. Type the molar mass, or just the formula, and fill in any two values.

Answer

Amount of substance (n)5.55093 mol
Number of particles (N)
3.34285 × 10²⁴ particles

n = m ÷ M, N = n × Nₐ (Nₐ = 6.02214076 × 10²³ per mole)

  1. Given (in base units): m = 100 g, M = 18.015 g/mol
  2. n = m ÷ M = 5.55093 mol
  3. N = n × Nₐ = 3.34285 × 10²⁴ particles
  • H2O: 18.015 g/mol, from IUPAC standard atomic weights.

Values

Fill in any 2; leave the ones to work out empty.

How is this calculated?
n = m ÷ M (moles = mass ÷ molar mass), and N = n × Nₐ (particles = moles × Avogadro constant), with Nₐ = 6.02214076 × 10²³ mol⁻¹ exactly.

Runs in your browser — nothing you enter leaves this device.

About this tool

What it does

Mole Calculator converts between the three ways chemists count an amount of substance: its mass in grams, the number of moles, and the number of particles — atoms, molecules or formula units. Fill in any two of mass, molar mass, moles and particles and the other two are worked out, with the formula and the working shown. The molar mass field takes a number in g/mol, or simply the chemical formula: type H2O, NaCl, C6H12O6 or CuSO4·5H2O and it is worked out from IUPAC’s standard atomic weights, with a note saying so. Particle counts can be typed in scientific notation, such as 3.01 × 10^23 or 3.01e23. The page uses the Avogadro constant as fixed by the 2019 redefinition of the SI: exactly 6.02214076 × 10²³ particles per mole.

How to use it
  1. Type two values: for example a mass and a formula, or a number of moles and a formula.
  2. Leave the other two empty; both are worked out and highlighted.
  3. Choose units: grams, milligrams or kilograms; moles, millimoles or micromoles.
  4. Read the working under the answer, including the molar mass used.
Limits and your data
  • Moles and particles describe the same amount, so giving both is refused: one of them must come with a mass or a molar mass.
  • The formula must be the exact substance weighed. A hydrate such as CuSO4·5H2O is much heavier per mole than the dry salt.
  • “Particles” means whatever the formula describes. For NaCl that is formula units; each contains two ions, so the number of ions is twice the answer.
  • Atomic weights are IUPAC’s abridged standard values to five significant figures, which is right for laboratory work; isotope-enriched material differs.
  • Everything is calculated in your browser. The formulas and amounts you type are not sent or saved.

Questions

How do I convert grams to moles?

Divide the mass by the molar mass. Type the mass and the formula: 100 g of water (H2O, 18.015 g/mol) is 5.551 mol — the page opens with this example.

How many molecules are in a mole?

Exactly 6.02214076 × 10²³, the Avogadro constant. Since 2019 this number defines the mole, rather than being measured.

How do I convert moles to grams?

Multiply by the molar mass. Enter the moles and the formula and leave mass empty: 2 mol of NaCl is 116.88 g.

How many atoms are in 12 g of carbon?

About 6.0166 × 10²³ — not exactly Avogadro’s number, because carbon’s standard atomic weight is 12.011, not 12. Natural carbon contains about 1.1% carbon-13.