A mole (mol) is 6.022×10²³ particles (Avogadro's number). It is the SI unit for amount of substance — the bridge between atomic and macroscopic scales.

How do I find the molar mass?

Add up the atomic masses of all atoms in the formula. H₂O: 2×1.008 + 15.999 = 18.015 g/mol. Use the IUPAC periodic table for accurate values.

Moles to Grams Calculator

Convert moles to grams by entering moles and molar mass. Formula: mass (g) = moles × molar mass (g/mol). For education only.

By AbraCalc Editorial Team · Reviewed by AbraCalc Methodology Review · Last reviewed: 2026-06-25 2 sources

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APA

AbraCalc. (2026). Moles to Grams Calculator [Online calculator]. Retrieved from https://abracalc.com/calculator/moles-to-grams-calculator/

BibTeX

@misc{abracalc-moles-to-grams-calculator, author = {AbraCalc}, title = {Moles to Grams Calculator}, year = {2026}, howpublished = {\url{https://abracalc.com/calculator/moles-to-grams-calculator/}} }

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How to use this tool

Enter amount (moles) and molar mass in the fields above.
Results update instantly as you type — or click Calculate.
Read your mass and the full breakdown beneath it.

To convert moles to grams use: mass = moles × molar mass. The molar mass is the atomic/molecular weight in g/mol, found on the periodic table. For example, 2 mol of water (18.015 g/mol) = 36.03 g.

For education only.

Formula

mass (g) = moles × molar mass (g/mol)

Millimoles: mmol = moles × 1000

How it works

This calculator multiplies the number of moles of a substance by its molar mass to give the equivalent mass in grams — the fundamental stoichiometry conversion used throughout chemistry. Molar mass is the mass of one mole of a substance, typically expressed in g/mol and found on the periodic table or from a compound's formula weight.

Results are rounded to four decimal places. The calculation assumes a pure substance; real-world samples may contain impurities that affect the measured mass.

Worked example

Worked example: mass of 2 mol of water

Identify inputs: moles = 2.0 mol, molar mass of H₂O = 18.015 g/mol.
Apply the formula: mass = 2.0 × 18.015 = 36.03 g.
Convert to millimoles: mmol = 2.0 × 1000 = 2000 mmol.

Mass = 36.03 g; Millimoles = 2000.0 mmol

Common mistakes to avoid

Using an approximate molar mass (e.g. 18 g/mol for water) instead of the more precise 18.015, which accumulates error in multi-step calculations.
Confusing molar mass with atomic number -- molar mass is in g/mol and found from the periodic table, not the element's atomic number.
Entering millimoles and treating them as moles -- 250 mmol = 0.250 mol; always confirm which unit the problem provides.

Key terms

Mole (mol): The SI unit for amount of substance; one mole contains exactly 6.022 × 10²³ particles (Avogadro's number).
Molar mass: The mass of one mole of a substance, expressed in g/mol; numerically equal to the relative molecular (or atomic) mass.
Millimole (mmol): One thousandth of a mole (0.001 mol); commonly used in laboratory and clinical settings for small quantities.
Stoichiometry: The quantitative relationship between reactants and products in a chemical reaction, based on the mole concept.

Frequently asked questions

What is a mole?: A mole (mol) is 6.022×10²³ particles (Avogadro's number). It is the SI unit for amount of substance — the bridge between atomic and macroscopic scales.
How do I find the molar mass?: Add up the atomic masses of all atoms in the formula. H₂O: 2×1.008 + 15.999 = 18.015 g/mol. Use the IUPAC periodic table for accurate values.