Molar Mass Calculator
Calculate molar mass (molecular weight) of any chemical formula with this free online molar mass calculator — element breakdown, mass percent, grams to moles.
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How to use Molar Mass Calculator
- 1Type a chemical formula such as H2O, Ca(OH)2 or CuSO4·5H2O — capital letters matter
- 2Read the molar mass in g/mol and the breakdown with each element's count, mass and mass percent
- 3Enter a mass in grams to convert it to moles and number of molecules
Frequently asked questions
How do you calculate molar mass?▾
Add up the atomic masses of every atom in the formula. For water (H2O): 2 × 1.008 (hydrogen) + 15.999 (oxygen) = 18.015 g/mol. The calculator does this for any formula and shows each element's share.
What is the molar mass of water?▾
18.015 g/mol — two hydrogen atoms (2 × 1.008) plus one oxygen atom (15.999). One mole of water, about 18 grams, contains 6.022 × 10²³ molecules.
How do I convert grams to moles?▾
Divide the mass by the molar mass: moles = grams ÷ g/mol. For example, 10 g of glucose (180.156 g/mol) is 0.0555 mol. Multiply moles by Avogadro's number (6.022 × 10²³) to get the number of molecules.
What is mass percent composition?▾
It's the share of a compound's mass that comes from each element: (element's total mass ÷ molar mass) × 100. In water, hydrogen is 11.19% and oxygen 88.81% by mass.
How do I enter hydrates and brackets?▾
Use parentheses or square brackets with a count after them, like Ca(OH)2 or K4[Fe(CN)6]. For hydrates, separate the water with ·, * or a dot: CuSO4·5H2O, CuSO4*5H2O or CuSO4.5H2O.
What's the difference between molar mass and molecular weight?▾
They're numerically the same. Molar mass is measured in grams per mole (g/mol); molecular weight (or molecular mass) is expressed in atomic mass units (u or Da) for a single molecule.
Embed Molar Mass Calculator on your website▾
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