Molar Mass Calculator

Accurate molecular weight calculator. Supports complex formulas with parentheses like Ca(NO₃)₂.

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Enter a chemical formula to see the full breakdown, mass percentages, and atomic analysis.

The Weight of Atoms

Molar Mass is the single most useful number in chemistry. It unlocks the ability to count invisible atoms by simply weighing them on a scale.

Concept Visualization

12.01 g
Carbon
1 Mole (Weight on Scale)
6.022 ×10²³
Atoms
Avogadro's Number

The Molar Mass tells you how heavy one "pack" (mole) of atoms is.

Periodic Table Math

Calculating Molar Mass is essentially a shopping receipt. You list every item (atom), its price (atomic mass), and quantity (subscript).

Glucose Receipt ($C_6H_12O_6$)

Carbon ($12.01$)x 6 = 72.06
Hydrogen ($1.008$)x 12 = 12.10
Oxygen ($16.00$)x 6 = 96.00
TOTAL180.16 g/mol

Why Decimals?

Why is Carbon 12.011 and not exactly 12?

This is because of Isotopes. Most Carbon atoms are Carbon-12 (mass 12), but about 1.1% are Carbon-13 (mass 13).

The number on the periodic table is a Weighted Average of all the isotopes found in nature. This ensures that when you scoop up a handful of carbon, the mass calculation is accurate for that real-world sample.

Common Molar Masses

Water ($H_2O$)18.02 g/mol
Methane ($CH_4$)16.04 g/mol
Salt ($NaCl$)58.44 g/mol
Sulfuric Acid ($H_2SO_4$)98.08 g/mol
Glucose ($C_6H_{12}O_6$)180.16 g/mol
Caffeine ($C_8H_{10}N_4O_2$)194.19 g/mol

Explore More Chemistry Tools

Mole Calculator

Grams to Moles conversion.

Stoichiometry

Reactant calculations.

Molarity

Concentration of solutions.

Frequently Asked Questions

What is Molar Mass?

Molar Mass is the mass of exactly one mole ($6.022 \times 10^{23}$ particles) of a substance. It is expressed in units of grams per mole (g/mol). It is the bridge between the weight you measure on a scale and the number of atoms reacting.

Is it the same as Molecular Weight?

Practically, yes. Molecular Weight is the mass of a single molecule in amu (atomic mass units). Molar Mass is the mass of a mole in grams. Because $1 \text{ g} = 6.022 \times 10^{23} \text{ amu}$, the numerical values are identical.

How do I calculate it manually?
  1. Find the Atomic Mass of each element on the Periodic Table.
  2. Multiply each mass by the subscript (number of atoms).
  3. Add them all together. Example $H_2O$: $(1.008 \times 2) + 16.00 = 18.016$ g/mol.
How do parentheses work? e.g., $Ca(NO_3)_2$

The number outside the parenthesis multiplies everything inside. In $Ca(NO_3)_2$, you have 1 Calcium, 2 Nitrogens ($1 \times 2$), and 6 Oxygens ($3 \times 2$).

What about Isotopes?

The Periodic Table values are Weighted Averages. Carbon is listed as 12.011, not 12.000, because 1.1% of Carbon on Earth is Carbon-13. This calculator uses standard weighted atomic masses.

How do hydrates work? e.g., $CuSO_4 \cdot 5H_2O$

The dot ($\cdot$) adds the water mass to the total. $CuSO_4$ (159.6) + $5 \times H_2O$ ($5 \times 18.0$) = $249.6$ g/mol. Treat water as a single unit or add the atoms ($H_{10}O_5$) to the formula.

Why is Molar Mass important in stoichiometry?

Reactions happen atom-to-atom, not gram-to-gram. If you want to react 1 mole of A with 1 mole of B, you must weigh different amounts determined by their molar masses. It is the conversion factor between Mass and Moles.

Does temperature affect Molar Mass?

No. Mass is an intrinsic property of the atoms. Unlike volume or density, molar mass is constant regardless of temperature or pressure.

Can I use this for proteins?

Yes, but typing the formula for a protein ($C_{400}H_{620}...$) is tedious. Biochemists usually measure protein mass in Daltons (Da) using electrophoresis or mass spectrometry.

What is Formula Weight?

It is a synonym for Molar Mass, often used for ionic compounds (like NaCl) that don't technically form discrete molecules. The calculation method is exactly the same.