Molar Mass Calculator

Calculate the molar mass of any chemical compound in grams per mole (g/mol) from its molecular formula — fast, accurate, and free.

Try:
Molecular Weight
0.000 g/mol
Calculation Breakdown
Element Atomic Mass Atoms Total %
Total Molecular Weight
Elements in this compound
In formula
Other elements

Quick Examples

Click any compound to calculate its molecular weight instantly.

Water
H₂O
18.015 g/mol
Carbon Dioxide
CO₂
44.009 g/mol
Sodium Chloride
NaCl
58.443 g/mol
Glucose
C₆H₁₂O₆
180.156 g/mol
Ethanol
C₂H₅OH
46.069 g/mol
Sulfuric Acid
H₂SO₄
98.077 g/mol

How to Use the Molar Mass Calculator

To find the molar mass of any compound, enter its chemical formula into the input field above and click "Calculate." The calculator returns the total molar mass in grams per mole along with a breakdown of each element's contribution.

Follow these 4 steps to calculate molar mass using this tool:

  1. Type the chemical formula of your compound into the input field. Use standard notation: uppercase for the first letter of each element symbol, lowercase for the second (e.g., "Na" for sodium, not "NA").
  2. Include subscript numbers directly after each element to indicate atom count. For example, enter "H2O" for water or "C6H12O6" for glucose.
  3. Press "Calculate Molecular Weight" or hit Enter. The calculator parses the formula and looks up each element's standard atomic weight from the IUPAC periodic table data.
  4. Read the result displayed in g/mol. The breakdown table below the result shows each element's atomic mass, atom count, subtotal mass, and percentage contribution to the compound.

The calculator handles parentheses like Ca(OH)₂ and hydrates like CuSO₄·5H₂O. It multiplies atoms inside parentheses by the subscript that follows and adds the mass of water molecules in hydrated compounds.

How the Molar Mass Calculator Works

The molar mass calculator determines the mass of one mole of a substance by summing the standard atomic weights of every atom specified in the chemical formula. One mole equals exactly 6.02214076 × 10²³ particles (Avogadro's number), making molar mass the bridge between atomic-scale measurements and laboratory-scale quantities.

The calculation follows this formula:

M
Molar Mass Formula
M = Σ (nᵢ × Aᵢ), where nᵢ is the number of atoms of element i, and Aᵢ is the standard atomic weight of element i in g/mol.
In
Inputs Required
A valid chemical formula using standard element symbols and subscript numbers. Examples: NaCl, H₂SO₄, C₆H₁₂O₆.
Out
Output Provided
Total molar mass in g/mol, plus a per-element breakdown showing atomic mass, atom count, subtotal contribution, and weight percentage.
Ref
Data Source
Standard atomic weights are sourced from IUPAC's most recent abridged values, which reflect natural isotopic abundances averaged across terrestrial samples.

For a compound like sulfuric acid (H₂SO₄), the calculation works as follows: Hydrogen contributes 2 × 1.008 = 2.016 g/mol. Sulfur contributes 1 × 32.06 = 32.06 g/mol. Oxygen contributes 4 × 15.999 = 63.996 g/mol. The total molar mass is 2.016 + 32.06 + 63.996 = 98.072 g/mol.

Molar mass is used directly in stoichiometry calculations, solution preparation, and concentration conversions. Knowing the molar mass of a reactant or product lets chemists convert between grams and moles: moles = mass (g) ÷ molar mass (g/mol).

Common Compound Molecular Weights

Reference table of frequently searched chemical compounds.

Chemical Formula Compound Name Molecular Weight
H₂O Water 18.015 g/mol
CO₂ Carbon Dioxide 44.009 g/mol
NaCl Sodium Chloride 58.443 g/mol
NH₃ Ammonia 17.031 g/mol
CH₄ Methane 16.043 g/mol
H₂SO₄ Sulfuric Acid 98.077 g/mol
CaCO₃ Calcium Carbonate 100.086 g/mol
C₆H₁₂O₆ Glucose 180.156 g/mol
C₂H₅OH Ethanol 46.069 g/mol
HCl Hydrochloric Acid 36.461 g/mol
NaOH Sodium Hydroxide 39.997 g/mol
Ca(OH)₂ Calcium Hydroxide 74.092 g/mol
HNO₃ Nitric Acid 63.012 g/mol
KMnO₄ Potassium Permanganate 158.032 g/mol
CuSO₄ Copper(II) Sulfate 159.607 g/mol

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Molar Mass Calculator FAQs and Common Questions

Answers to frequently asked questions about calculating molar mass, units, accuracy, and practical uses.

What is molar mass and how is it different from molecular weight?
Molar mass is the mass of one mole (6.022 × 10²³ particles) of a substance, measured in grams per mole (g/mol). Molecular weight is a dimensionless ratio comparing a molecule's mass to 1/12th of a carbon-12 atom. Both share the same numerical value for most practical calculations, but molar mass carries the unit g/mol, making it directly usable for lab measurements.
How do I calculate molar mass from a chemical formula?
To calculate molar mass from a chemical formula, identify each element and its subscript count in the formula. Multiply each element's standard atomic weight by the number of atoms present. Sum all the products. The result is the molar mass in g/mol. For example, for H₂O: (2 × 1.008) + (1 × 15.999) = 18.015 g/mol.
What units are used for molar mass?
Molar mass is expressed in grams per mole (g/mol). This unit connects mass on a laboratory scale to the number of particles at the molecular level through Avogadro's number (6.022 × 10²³). Some sources also express molar mass in kilograms per mole (kg/mol) for larger-scale industrial calculations.
Can this calculator find molar mass for ionic compounds?
Yes. The calculator accepts any valid chemical formula, including ionic compounds like NaCl or CaCO₃. For ionic substances, the term "formula mass" is technically more precise since discrete molecules do not exist, but the numerical calculation method is identical: sum the atomic weights of all atoms in one formula unit.
Why do molar mass values vary slightly between different sources?
Molar mass values can differ slightly because standard atomic weights published by IUPAC are periodically updated as isotopic abundance measurements improve. Different sources may use older datasets or round values to different decimal places. This calculator uses the most recent IUPAC abridged standard atomic weights.
What is the molar mass of water (H₂O)?
The molar mass of water (H₂O) is 18.015 g/mol. This value comes from adding the atomic weights of two hydrogen atoms (2 × 1.008 = 2.016 g/mol) and one oxygen atom (15.999 g/mol).