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Mole to Grams

ChemistryStoichiometry and Reactions
Mass —
Substance
—
Molar mass (g/mol)
—
Mass in kilograms
—
Number of particles
—

To convert moles to grams, multiply the amount in moles by the substance's molar mass in g/mol. For water, with a molar mass of 18.015 g/mol, 2 mol × 18.015 g/mol = 36.03 g. The molar mass is the sum of the atomic weights in one formula unit, read from the periodic table.

About this tool

Chemistry students, lab technicians and anyone preparing a reaction often know how many moles they need but must weigh the material on a balance in grams. This calculator does that conversion. Choose one of six common compounds with preset molar masses, or pick Other and type the molar mass of any substance. The result shows the mass in grams and kilograms, the molar mass used, and the number of particles from Avogadro's constant, with the working written out. One limit: it does not work out molar mass from a chemical formula, so for an unlisted compound you need to add up the atomic weights first, or use a molecular mass calculator.

How to use it

  1. Choose the substance

    Pick a listed compound, or Other to enter a molar mass yourself.

  2. Enter the molar mass if needed

    For Other, type the molar mass in g/mol, e.g. 74.55 for potassium chloride.

  3. Enter the amount in moles

    Type the number of moles; the mass in grams updates as you type.

  4. Read the working

    Check the molar mass, kilograms and particle count shown under the result.

Examples

2 mol of water

Substance
Water (H2O)
Amount of substance
2

Result Mass: 36.03
Substance: Water (H2O)
Molar mass (g/mol): 18.015
Mass in kilograms: 0.03603
Number of particles: 1.2044e+24 particles

  1. Molar mass of Water (H2O) = 18.015 g/mol
  2. Mass = 2 mol × 18.015 g/mol = 36.03 g
  3. Particles = 2 mol × 6.02214076 × 10^23 = 1.2044e+24

Water's molar mass is 18.015 g/mol, so two moles weigh just over 36 grams, about two tablespoons.

0.5 mol of glucose

Substance
Glucose
Amount of substance
0.5

Result Mass: 90.078
Substance: Glucose (C6H12O6)
Molar mass (g/mol): 180.156
Mass in kilograms: 0.090078
Number of particles: 3.0111e+23 particles

  1. Molar mass of Glucose (C6H12O6) = 180.156 g/mol
  2. Mass = 0.5 mol × 180.156 g/mol = 90.078 g
  3. Particles = 0.5 mol × 6.02214076 × 10^23 = 3.0111e+23

Glucose is 180.156 g/mol, so half a mole is about 90 g.

0.25 mol of KCl (74.55 g/mol)

Substance
Other (enter molar mass)
Molar mass
74.55
Amount of substance
0.25

Result Mass: 18.6375
Substance: Custom substance
Molar mass (g/mol): 74.55
Mass in kilograms: 0.018638
Number of particles: 1.5055e+23 particles

  1. Molar mass of Custom substance = 74.55 g/mol
  2. Mass = 0.25 mol × 74.55 g/mol = 18.6375 g
  3. Particles = 0.25 mol × 6.02214076 × 10^23 = 1.5055e+23

Potassium chloride is not in the list, so its molar mass is typed in: 0.25 × 74.55 = 18.6375 g.

How it is calculated

m = n × M

m
mass in grams
n
amount of substance in moles
M
molar mass in g/mol

A mole is exactly 6.02214076 × 10^23 particles. The molar mass M is the mass of one mole and equals the sum of the standard atomic weights in the formula, so multiplying n by M gives grams. The preset values use IUPAC standard atomic weights rounded to three decimals. The particle count is n multiplied by the Avogadro constant.

When not to use it

  • Do not use it for solutions where you know concentration and volume; find moles from molarity first.
  • Isotopically enriched samples have a different molar mass from the standard atomic weights.
  • Hydrated salts need the water of crystallisation included in the molar mass.

Common mistakes

  • Using the atomic mass of one element instead of the whole compound's molar mass.
  • Forgetting the subscripts, such as counting one hydrogen in H2O instead of two.
  • Entering millimoles as moles, which makes the mass 1,000 times too large.

Frequently asked questions

What is the formula for converting moles to grams?

Mass in grams equals moles multiplied by molar mass in g/mol. The mol units cancel, leaving grams. For 3 mol of carbon dioxide at 44.009 g/mol, the mass is 132.027 g.

Where do I find a compound's molar mass?

Add up the standard atomic weights from the periodic table, each multiplied by its subscript. Sodium chloride is 22.990 + 35.45 = 58.44 g/mol. Sulfuric acid is 2(1.008) + 32.06 + 4(15.999) = 98.079 g/mol.

How do I go from grams back to moles?

Divide the mass by the molar mass instead of multiplying. 36.03 g of water divided by 18.015 g/mol gives 2 mol. The grams to moles tool does this direction.

Why is the number of particles shown?

One mole holds 6.02214076 × 10^23 particles by definition since the 2019 SI redefinition. Showing the count helps when a problem asks for molecules, atoms or formula units rather than mass.

What about a hydrate such as copper sulfate pentahydrate?

Include the water molecules in the molar mass. CuSO4·5H2O is about 249.69 g/mol, not the 159.61 g/mol of anhydrous copper sulfate. Choose Other and type the hydrate value.

Does temperature or pressure change the result?

No. Mass and moles are both independent of conditions, so the conversion holds for solids, liquids and gases alike. Temperature matters only when you go from moles to a gas volume.

Cite this tool

Using this tool in an assignment, article or report? Copy a citation, or a link for your website.

APA

Tools Directory Editorial Team. (2026, October 23). Mole to Grams. Tools Directory. Retrieved October 27, 2026, from https://tools.milunir.com/chemistry/stoichiometry-and-reactions/mole-to-grams/

MLA

Tools Directory Editorial Team. “Mole to Grams.” Tools Directory, 23 Oct. 2026, https://tools.milunir.com/chemistry/stoichiometry-and-reactions/mole-to-grams/. Accessed 27 Oct. 2026.

Chicago

Tools Directory Editorial Team. “Mole to Grams.” Tools Directory. Last modified October 23, 2026. Accessed October 27, 2026. https://tools.milunir.com/chemistry/stoichiometry-and-reactions/mole-to-grams/.

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