How does this molar mass calculator work?

Enter a formula such as H2O, NaCl, or Ca(OH)2, or type a common compound name. The calculator expands parentheses, counts atoms, multiplies by standard atomic masses, and reports the total with an element-by-element breakdown.

Can I calculate molar mass of H₂O and water the same way?

Yes. Water and H₂O refer to the same substance. Searching either name or formula returns 18.015 g/mol and the same atom contributions.

Does the calculator handle parentheses and hydrates?

Yes. Parentheses multiply every atom inside the group, and formulas such as CuSO4·5H2O can be entered when supported by the parser. Always expand hydrates carefully on paper too.

Is molar mass the same as molecular weight?

They are numerically equal for a given formula. Chemistry courses usually expect molar mass in g/mol, while molecular weight is often treated as a relative, unitless number.

Molar Mass Calculator

Calculate molar mass from any chemical formula or compound name. Get an instant result in g/mol, an element-by-element breakdown, and links to full study pages for water, NaCl, H₂SO₄, and other common compounds.

Live molar mass calculator

Supports parentheses, polyatomic groups, and common names such as water, sodium chloride, and ethanol.

What is a molar mass calculator?

A molar mass calculator is an educational tool that converts a chemical formula into the mass of one mole of that substance. Chemists report that value in grams per mole (g/mol). Students use it to check homework, prepare solutions, and solve stoichiometry problems without looking up every atomic mass by hand.

This calculator is designed for learning: it shows how each element contributes to the total, so you can see why the molar mass of H₂O is about 18 g/mol and why NaCl is about 58.4 g/mol.

How does the calculator work?

Parse the formula and expand parentheses.
Count atoms of each element.
Multiply atom counts by standard atomic masses.
Add the contributions to report total molar mass in g/mol.

The same method works whether you search for “water” or enter H₂O, and whether you study CO₂, NH₃, or CaCO₃.

How to calculate molar mass manually

Use the periodic table, count atoms carefully, and keep units. For a full walkthrough, read how to calculate molar mass and what is molar mass.

Step-by-step method

Write the chemical formula clearly.
List each element and its atom count.
Look up each atomic mass.
Multiply, then add all contributions.
Report the answer with the unit g/mol.

Worked examples

Example 1: Molar mass of water (H₂O)

H₂O has 2 H and 1 O. (2 × 1.008) + 15.999 = 18.015 g/mol. Oxygen contributes most of the mass even though hydrogen atoms are more numerous.

Example 2: Molar mass of sodium chloride (NaCl)

NaCl has 1 Na and 1 Cl. 22.990 + 35.45 = 58.44 g/mol. This value is used constantly in solution preparation and saline calculations.

Example 3: Molar mass of sulfuric acid (H₂SO₄)

H₂SO₄ has 2 H, 1 S, and 4 O. (2 × 1.008) + 32.06 + (4 × 15.999) ≈ 98.07 g/mol. Parentheses are not required here, but atom counting still matters.

Example 4: Parentheses — Ca(OH)₂

In Ca(OH)₂, the subscript 2 multiplies both O and H. Atom counts: 1 Ca, 2 O, 2 H. Students who forget to expand parentheses undercount the molar mass.

Common student mistakes

Forgetting that parentheses multiply every atom inside the group.
Rounding atomic masses too early on multi-element formulas.
Reporting a number without the unit g/mol.
Confusing elemental atomic mass with the molar mass of a diatomic gas such as O₂ or Cl₂.
Dropping hydrate water from formulas such as CuSO₄·5H₂O.

Study the full list in our common molar mass mistakes guide.

Applications in chemistry

Laboratory uses

Laboratory work depends on converting grams on a balance into moles for titration, buffer preparation, and limiting-reactant experiments. Accurate molar mass is the bridge between those units.

Industrial uses

Industrial batching, fertilizer grades, and quality-control assays scale the same mole arithmetic from grams to kilograms and tonnes. See also stoichiometry basics and laboratory calculations.

Why molar mass matters

Without molar mass, balanced equations cannot be connected to weighable amounts of chemicals. It is the conversion students use in nearly every quantitative chemistry problem after the mole concept itself.

Practice examples

Calculate the molar mass of CH₄ and of methane by name — confirm both routes match.
Find the molar mass of NH₃, then compute grams in 0.50 mol of ammonia.
Expand Al₂(SO₄)₃ carefully and total the molar mass.

More worksheets are available on the practice hub.

Related chemistry guides

Related compounds

Open a full profile when you need properties, reactions, and practice beyond the calculator result:

Browse the full compound library, periodic table, and reference tables.

Frequently asked questions

A molar mass calculator converts a chemical formula into grams per mole (g/mol) by adding the atomic masses of every atom in the formula. It is the fastest way to check homework and prepare laboratory solutions.

References

IUPAC standard atomic weights for classroom and laboratory molar mass calculations.
Site method notes: How we calculate and scientific accuracy policy.
Supporting articles in the chemistry articles library.