Grams to Moles Calculator
Convert a mass in grams into the number of moles by dividing by the substance molar mass.
g
g/mol
Molar mass computed from formula: 18.015 g/mol
- 1
Molar mass (M)
18.015 g/molComputed by summing standard atomic weights from the chemical formula. - 2
Moles = mass ÷ molar mass
18 g ÷ 18.015 g/mol = 0.9992 mol
How does this calculator work?
To convert grams to moles, divide the mass in grams by the molar mass in grams per mole: n = m / M. Enter the molar mass directly, or type a chemical formula like H2O and the calculator sums standard atomic weights to find M, then reports the amount of substance in moles.
Formula
How this is calculated
The number of moles n equals the sample mass m divided by the molar mass M of the substance: n = m / M. Mass is entered in grams and the molar mass in grams per mole, so the result is in moles. One mole is Avogadro number of particles, 6.02214076 x 10^23.
You can supply the molar mass directly, or leave it blank and enter a chemical formula such as H2O, NaCl, C6H12O6 or Ca(OH)2. The calculator then sums standard atomic weights for every atom in the formula (expanding parenthesised groups and their multipliers) to obtain M automatically. The molar mass field always takes priority when it is filled in.
Assumptions and edge cases: mass must be zero or positive, and molar mass must be strictly positive, so a blank or unrecognised formula yields no result. The atomic-weight table uses abridged IUPAC standard values, so molar masses are accurate to roughly four significant figures. Hydrates, isotopes and charge are not modelled.
Frequently asked questions
Either type it directly in g/mol, or enter the chemical formula and let the calculator sum the standard atomic weights of each atom.
Water (H2O) has a molar mass of about 18.015 g/mol, so 18 g of water is roughly 1 mole.
Yes. Formulas with parentheses like Ca(OH)2 are expanded automatically before summing atomic weights.
Also known as
TG we-Calculate Editorial Team. (2026). Grams to Moles Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/grams-to-moles-calculator
TG we-Calculate Editorial Team. "Grams to Moles Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/grams-to-moles-calculator.
TG we-Calculate Editorial Team, "Grams to Moles Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/grams-to-moles-calculator
@misc{wecalculate_grams_to_moles_calculator, title = {Grams to Moles Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/grams-to-moles-calculator}}, year = {2026}, note = {TG we-Calculate} }
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