Molar Mass Calculator

Enter a chemical formula such as Ca(OH)2 and get its molar mass in g/mol with a per-element breakdown. Calculates in your browser.

Use element symbols and counts, e.g. H2O, CuSO4, Ca(OH)2.

Molar mass

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Show the math

Molar mass is the sum of each element's atomic weight times how many atoms appear:

M = Σ (atoms × atomic weight)

Atomic weights are the IUPAC standard values in g/mol. All math runs in your browser.

What this does

A molar mass calculator takes a chemical formula such as Ca(OH)2 and returns its molar mass in g/mol with a per-element breakdown.

How to use it

  1. Type the chemical formula.
  2. Use parentheses for groups.
  3. Read the molar mass in g/mol.
  4. Check the per-element breakdown.

How it works

Each element’s standard atomic weight is multiplied by how many atoms appear in the formula, then summed. Atomic weights use IUPAC standard values.

M = Σ (atoms × atomic weight)

Understanding your result

The molar mass is the bridge between grams in the lab and moles in an equation, so it is the number you weigh out by. The per-element breakdown shows which atoms dominate the mass, useful for checking a formula. It uses standard atomic weights, so isotopically unusual samples or hydrates (waters of crystallisation) will differ from the bare formula.

Example

Water (H2O) has a molar mass of about 18.02 g/mol.

Sources & methodology

Last updated .

Frequently asked questions

How is molar mass found?

Add up each element’s standard atomic weight times how many atoms appear in the formula: M = Σ (atoms × atomic weight).

What formulas are supported?

Element symbols with counts and parentheses, e.g. H2O, CuSO4, and Ca(OH)2. Atomic weights use IUPAC standard values.

Is my data stored?

No. Everything is calculated locally in your browser.