Moles from Mass
n = m / MLast updated:
Molar Mass Calculator
Calculate molar mass from chemical formulas instantly. Find molecular weight for any compound with periodic table element data. Free chemistry calculator tool.
Molar Mass Calculator
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Calculate molecular weight from chemical formulas
Use proper capitalization: Na, not NA or na
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Chemistry Fundamentals
Molar Mass Calculator: Formula, Stoichiometry & Applications
Parse chemical formulas automatically and convert between mass and moles for lab, process, and educational use.
Core Relation
n = m / M
Unit
g / mol
Basis
IUPAC Atomic Masses
Use
Stoichiometry & Dosing
Reviewed by: CalculatorApp Chemistry & Engineering Team
What Is Molar Mass?
Molar mass bridges atomic-scale chemistry and laboratory-scale measurements. It allows chemists and engineers to weigh out precise mole quantities for reactions, determine theoretical yields, prepare standard solutions, and connect mass data to structural molecular information. Accurate molar mass is fundamental to quantitative analytical chemistry.
Mass from Moles
m = n × MMolar Mass Sum
M = Σ(nᵢ × Aᵢ)Concentration Link
c = n / V| Compound Type | Molar Mass Range | Typical Field |
|---|---|---|
| Simple molecules (H₂O, CO₂) | 18–44 g/mol | Lab chemistry, gas behavior |
| Salts and ionic compounds | 50–400 g/mol | Solution prep, analytical chem |
| Organic compounds | Wide range | Pharmaceuticals, materials |
| Polymers | Very high (kDa+) | Materials science, coatings |
History Timeline
Early 1800s: Dalton develops atomic theory and relative atomic masses.
1811: Avogadro proposes equal volumes of gas contain equal molecules.
1860: Cannizzaro clarifies atomic and molecular weights at Karlsruhe congress.
1869: Mendeleev organizes elements by atomic mass in the periodic table.
1961: Carbon-12 standard adopted for atomic mass unit by IUPAC.
Modern era: High-resolution mass spectrometry enables ultra-precise molar mass measurement.
PubMed Chemistry & Health
Chemical compound health and toxicology studies.
WHO Chemical Safety
International chemical safety and risk guidance.
CDC Toxic Substances
Toxicological profiles for industrial chemicals.
NEJM Archive
Pharmacological and biochemical clinical research.
Myth: Molar mass and molecular weight are totally different.
Fact: They are numerically identical but expressed in different units (g/mol vs u).
Myth: Subscript errors are minor.
Fact: A single subscript error changes the molar mass and invalidates all downstream calculations.
Myth: Isotopes do not affect molar mass.
Fact: Molar mass reflects natural isotopic abundance averages, not a single isotope.
Myth: Average atomic masses are arbitrary.
Fact: They are carefully maintained by IUPAC based on measured terrestrial isotopic abundances.
FAQ (12)
What is molar mass?
Molar mass is the mass per mole of a substance, expressed in grams per mole (g/mol).
How is it calculated from a formula?
Sum the atomic masses of all atoms in the formula, multiplied by their subscript quantities.
What is the difference between molar mass and molecular mass?
Molecular mass is in atomic mass units (u); molar mass is numerically equal but expressed in g/mol.
Where do atomic masses come from?
They are derived from isotopic abundances weighted by abundance fraction, published by IUPAC.
Why is molar mass important for stoichiometry?
It converts between measurable mass and mole quantities essential for reaction calculations.
What is Avogadro's number's role?
One mole contains 6.022 × 10²³ particles, linking molar mass to atomic-scale properties.
How accurate is automatic formula parsing?
Parser handles standard chemical notation but verify unusual polyatomic or bracketed groups manually.
Can I use this for polymers?
For repeating-unit polymers, calculate the monomer molar mass then scale by degree of polymerization.
How does molar mass affect gas behavior?
In the ideal gas law, heavier molecules move slower at the same temperature (Maxwell-Boltzmann).
What affects precision?
Precision is determined by atomic mass table accuracy and correct compound formula entry.
Can I compute molar mass for mixtures?
For mixtures, compute a mole-fraction-weighted average molar mass.
What are typical use cases?
Solution preparation, reaction balancing, gas law calculations, analytical chemistry, and pharmaceutical dosing.
References
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