Molar Mass Calculator

92 Elements 47+ Compounds Live Calculation IUPAC 2021

Free molar mass calculator with elemental composition breakdown. Enter any chemical formula to get the molecular weight instantly. Supports parentheses, brackets, hydrates, and coefficients. Includes an interactive periodic table and 47+ pre-loaded compounds.

Calculate Molar Mass
Supports elements, parentheses, brackets, hydrate dot (·), and leading coefficients.

Molar Mass Result

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Enter a formula

Type a chemical formula above or click an example chip.

Interactive Periodic Table

Click elements to select them, then build a formula. All 92 elements with IUPAC 2021 atomic masses.

Common Compounds Library

Learn: Molar Mass

What Is Molar Mass?

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). One mole contains exactly 6.022 × 10²³ particles (Avogadro's number). It allows chemists to convert between mass and amount in chemical reactions.

How to Calculate

  1. Write the chemical formula of the compound.
  2. Identify all elements and count their atoms (including inside parentheses).
  3. Look up each element's atomic mass from the periodic table.
  4. Multiply atomic mass × number of atoms for each element.
  5. Add all values to get the total molar mass.
Example: H₂O = (2 × 1.008) + (1 × 15.999) = 18.015 g/mol

Molar Mass vs. Molecular Weight

Molar mass (g/mol) refers to the mass of 1 mole. Molecular weight (amu) refers to the mass of 1 molecule. Numerically they are the same — the difference is in units and context.

Supported Formula Syntax

  • Elements: H, O, C, Na, Fe, etc.
  • Subscripts: H2O, CO2, C6H12O6
  • Parentheses: Ca(OH)2, Al2(SO4)3
  • Brackets: [Cu(NH3)4]SO4
  • Hydrates: CuSO4·5H2O (use dot)
  • Coefficients: 3H2SO4 (3 molecules)

Tips & Common Mistakes

  • Don't forget to multiply subscripts inside parentheses: Ca(OH)₂ has 2 O and 2 H.
  • Coefficients multiply the entire formula: 3H₂SO₄ = 3 × 98.079 g/mol.
  • Always use IUPAC 2021 atomic masses for accuracy.
  • Round only at the final step to avoid cumulative errors.

1 What is Molar Mass?

Molar mass is the mass of one mole of a substance (chemical element or compound), expressed in grams per mole (g/mol). One mole contains exactly 6.022 × 10²³ particles (Avogadro's number), whether they are atoms, molecules, ions, or electrons. Molar mass allows chemists to convert between mass (grams) and amount (moles) in chemical reactions.

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Key insight: Numerically, molar mass (g/mol) equals molecular weight (amu). The difference is in units and context. This calculator uses IUPAC 2021 standard atomic weights for all 92 elements.

2 How to Calculate Molar Mass

Follow these five steps for any compound. This is the exact process our calculator automates:

1

Write Formula

Write the correct chemical formula for the compound.

2

Count Atoms

Identify all elements and count atoms, including inside parentheses.

3

Look Up Masses

Find each element's atomic mass from the periodic table.

4

Multiply

Atomic mass × number of atoms for each element.

5

Sum Total

Add all values to get the molar mass in g/mol.

3 Worked Examples

Water (H₂O):
H: 2 × 1.008 = 2.016  |  O: 1 × 15.999 = 15.999
Total: 18.015 g/mol
Sulfuric Acid (H₂SO₄):
H: 2 × 1.008 = 2.016  |  S: 1 × 32.06 = 32.06  |  O: 4 × 15.999 = 63.996
Total: 98.072 g/mol
Calcium Hydroxide Ca(OH)₂:
Ca: 1 × 40.078 = 40.078  |  O: 2 × 15.999 = 31.998  |  H: 2 × 1.008 = 2.016
Total: 74.092 g/mol
Copper Sulfate Pentahydrate CuSO₄·5H₂O:
CuSO₄: 63.546 + 32.06 + 63.996 = 159.602  |  5H₂O: 5 × 18.015 = 90.075
Total: 249.677 g/mol

4 Real-World Applications

  • Laboratory preparation: Weigh precise amounts of reagents for solutions and experiments.
  • Stoichiometry: Convert between grams and moles to predict reaction yields.
  • Pharmaceutical industry: Calculate precise drug dosages and active ingredient concentrations.
  • Environmental science: Measure CO₂ emissions and pollutant concentrations.

Frequently Asked Questions

Molar mass is the mass of one mole of a substance (g/mol). It is essential for converting between mass and moles in chemical calculations, preparing solutions with precise concentrations, and predicting reaction yields in stoichiometry.
The parser treats the dot (·) as a separator. It calculates the anhydrous part (CuSO₄ = 159.602 g/mol) and the hydrate part (5H₂O = 90.075 g/mol) then adds them together for the total (249.677 g/mol). All element counts are combined correctly.
Molar mass is expressed in g/mol and refers to the mass of 1 mole. Molecular weight is expressed in amu (atomic mass units) and refers to the mass of 1 molecule. Numerically they are the same — the difference is in units and context of use. For ionic compounds, the term "formula mass" is preferred.
Yes. A leading number is treated as a coefficient that multiplies all element counts. For example, 3H₂SO₄ = 3 × 98.079 = 294.237 g/mol. This is useful for stoichiometry when calculating total mass of multiple molecules.
Yes, 100% free with no signup. All computation runs entirely in your browser using JavaScript. No data is sent to any server. Features include interactive periodic table, 47+ compound library, shareable URLs, and clipboard copy.

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