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Molar Mass Calculator

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Elemento	Contar	Atomic Mass (g/mol)	Mass Contribution (g/mol)	% by Mass
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Molar Mass Calculator

Type a chemical formula and get the exact molar mass in g/mol, a per-element breakdown, and the mass percentage of each element. Atomic weights use IUPAC 2021 standard values so results are reliable for laboratory and coursework use. Parentheses, polyatomic groups, and hydrate notation (CuSO4·5H2O) are fully supported.

Cómo Usar

Enter a chemical formula in the input box (for example, C6H12O6 for glucose).
Pick an output unit: g/mol, kg/mol, or atomic mass units per molecule.
Set the number of decimal places (4 is standard for lab work).
Read the total molar mass from the summary card and review each element’s contribution and mass percentage in the table.
Haz clic en Copy Molar Mass to grab the formatted value for your notebook, paper, or LIMS record.

Supported Formula Syntax

Element symbols – case-sensitive, e.g. Co (cobalt) versus CO (carbon monoxide).
Subscripts – plain digits (H2O) or unicode subscripts (H₂O) both work.
Parentheses – nest polyatomic groups freely, e.g. Ca3(PO4)2 or Al2(SO4)3.
Hydrates – use a center dot or asterisk between parts, e.g. CuSO4·5H2O or MgSO4*7H2O.
Common compounds – click any quick-select pill to load a worked example.

Características

IUPAC 2021 atomic weights – conventional values used worldwide for stoichiometry, with sensible defaults for synthetic elements.
Per-element contribution table – count, atomic mass, mass contribution, and mass percent for every element in the formula.
Mass percent composition – instantly answer questions like “what fraction of glucose is carbon?”
Three output units – g/mol for solutions, kg/mol for polymer chemistry, amu/molecule for molecular-scale work.
Precisión configurable – from 0 to 8 decimal places, depending on how exact your answer needs to be.
Hydrate-aware parser – distinguishes the anhydrous formula from the water of crystallization.
Live calculation – the result updates as you type; no submit button to click.
Helpful error messages – flags unknown element symbols, unmatched parentheses, and empty hydrate sections.

 Preguntas frecuentes

What is molar mass and how is it different from molecular weight?

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). Molecular weight (or relative molecular mass) is a dimensionless ratio comparing the mass of a molecule to one-twelfth the mass of a carbon-12 atom. Numerically the two are equal — water is 18.015 g/mol and has a molecular weight of 18.015 — but molar mass carries the unit g/mol and connects the microscopic atomic scale to laboratory quantities you can actually weigh on a balance.
Why do atomic weights have decimal values that aren't whole numbers?

Most natural elements occur as a mixture of isotopes — atoms with the same number of protons but different numbers of neutrons. The atomic weight listed on a periodic table is the weighted average of the isotope masses, weighted by their natural abundance on Earth. Chlorine, for example, is roughly 76% chlorine-35 and 24% chlorine-37, which averages to 35.45 u. IUPAC reviews these values periodically and publishes recommended conventional weights for everyday chemistry.
What does the center dot (·) mean in a formula like CuSO4·5H2O?

The center dot separates the main compound from water molecules (or other small molecules) bound into the crystal structure. CuSO4·5H2O is copper(II) sulfate pentahydrate — one formula unit contains one CuSO4 and five waters of crystallization. The dot is not chemical bonding notation; it is shorthand for stoichiometry. When you compute molar mass, you simply add the mass of CuSO4 to five times the mass of H2O.
How do mole conversions actually work in stoichiometry?

One mole is Avogadro's number (6.022 × 10²³) of particles. Molar mass is the conversion factor between mass (measurable on a balance) and moles (the unit of chemical amount). To convert grams to moles, divide by molar mass. To convert moles back to grams, multiply by molar mass. In a balanced equation, the coefficients are mole ratios, which is why molar mass lets you predict reactant and product masses precisely.
Why is the molar mass percent composition useful?

Mass percent composition tells you what fraction of a compound's total mass comes from each element. It's the foundation for empirical formula determination from combustion analysis, for verifying purity of a synthesized compound, and for industrial calculations like nitrogen content in fertilizer or carbon content in steel. Two compounds with the same empirical formula share the same mass percent composition, regardless of molecular size.