Grams to Moles Calculator
This grams to moles calculator turns the mass of a substance into its amount in moles. Example: 36.03 g of water (M = 18.015 g/mol) is 2 mol.
Example: Direction: Grams to moles · Mass m 36.03 g · Molar mass M 18.015 g/mol → Result: 36.03 g = 2 mol (≈ 1.20443 × 10²⁴ particles). Source: NIST/CODATA – Avogadro constant N_A = 6.02214076 × 10²³ mol⁻¹ (exact since the 2019 SI revision). Updated: .
How it is calculated
One mole is the amount of substance that contains exactly 6.02214076 × 10²³ particles. The mass of one mole of a substance is its molar mass M in g/mol. That lets you convert between grams and moles, which every reaction calculation in chemistry requires.
Formulas
From the mass m you get the amount n = m / M. Conversely m = n · M. The number of particles is N = n · N_A with the Avogadro constant N_A = 6.02214076 × 10²³ per mole. You get the molar mass of a compound by adding the atomic masses of all atoms in the formula.
Worked example
Water (H₂O) has M = 2 · 1.008 + 15.999 = 18.015 g/mol. So 36.03 g of water is n = 36.03 / 18.015 = 2 mol. That corresponds to N = 2 · 6.02214076 × 10²³ ≈ 1.204 × 10²⁴ water molecules. Conversely, 0.25 mol of table salt (M = 58.44 g/mol) weighs 0.25 · 58.44 = 14.61 g.
- Look up atomic masses in the periodic table (IUPAC values, usually rounded to 3 or 4 digits).
- The molar mass is in g/mol, so the mass must be entered in grams.
- One mole of an ideal gas occupies about 22.4 L only at 0 °C and 101.325 kPa; under other conditions use the gas law.
Frequently asked questions
How do you convert grams to moles?
Divide the mass in grams by the molar mass in g/mol: n = m / M. In the example 36.03 g / 18.015 g/mol = 2 mol.
How do you calculate molar mass?
Add the atomic masses of all atoms in the formula. For H₂O: 2 · 1.008 + 15.999 = 18.015 g/mol.
How many particles are in one mole?
Exactly 6.02214076 × 10²³, the Avogadro constant. The number of particles N is therefore n times N_A.
Sources and legal basis
- NIST/CODATA – Avogadro constant N_A = 6.02214076 × 10²³ mol⁻¹ (exact since the 2019 SI revision)
- IUPAC Green Book – Amount of substance (n = m / M)
- IUPAC – Atomgewichte (H 1,008, O 15,999 → H₂O 18,015 g/mol)
As of: · Editorial policy
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