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Molar Mass Calculator

Calculate the molar mass of a chemical formula and its composition by mass, with brackets and hydrates.

Case matters: Co is cobalt, CO is carbon monoxide. Brackets and hydrates work: Ca(OH)2, CuSO4·5H2O.

Result

Molar mass

180.156g/mol

Composition by mass

ElementAtomsMass (g/mol)Share
Carbon (C)672.06640%
Hydrogen (H)1212.0966.71%
Oxygen (O)695.99453.28%

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How the Molar Mass Calculator works

Type a chemical formula with correct capitals — Co is cobalt, CO is carbon monoxide. The calculator counts every atom, including those in brackets (Ca(OH)₂, K₄[Fe(CN)₆]) and hydrates written with a dot (CuSO₄·5H₂O), and adds up the standard atomic weights to give the molar mass in grams per mole, with each element's share by mass.

Formulas

Molar mass

M = Σ (atoms of each element × its atomic weight)

Mass share

% = element mass ÷ molar mass × 100

Examples

Water, H₂O

2 × 1.008 + 15.999 = 18.015 g/mol; oxygen is 88.81% of the mass.

Glucose and copper sulfate

C₆H₁₂O₆ is 180.156 g/mol; the hydrate CuSO₄·5H₂O is about 249.68 g/mol.

Frequently asked questions

Is molar mass the same as molecular weight?

Numerically yes: molar mass is in g/mol, molecular weight in atomic mass units (u).

Which atomic weights are used?

IUPAC standard atomic weights. For elements with no stable isotopes, the mass number of the longest-lived isotope.

How do I convert grams to moles?

Divide the mass in grams by the molar mass: 36.03 g of water is 2 moles.

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