⚗️ Molar Mass Calculator
Determine molecular weight, elemental counts, and mass contribution for any chemical formula.
Supports nested parentheses and integer subscripts. Examples: H2O, Ca(OH)2, Fe2(SO4)3, (NH4)2CO3.
How to Use This Calculator
Write the chemical formula
Type the molecular or empirical formula exactly as you would on paper, using parentheses to group polyatomic ions or hydrates.
Click “Calculate”
The parser interprets each element, applies subscripts, and expands any groups within parentheses before adding masses.
Review the results
The summary displays total molar mass, number of atoms of each element, mass contributions, and percent composition for quick lab reporting.
Export or copy data
Use the tabulated breakdown to document calculations in lab notebooks, safety data sheets, or stoichiometric problem sets.
Formula
Molar Mass = \u2211i (ni \u00d7 Mi)
ni is the number of atoms of element i in the formula unit, and Mi is the standard atomic mass of element i in unified atomic mass units (u). The calculator multiplies each atomic mass by its corresponding stoichiometric coefficient and sums the contributions.
Example: Calcium hydroxide, Ca(OH)2
nCa = 1, MCa = 40.078 → 40.078 g/mol
nO = 2, MO = 15.999 → 31.998 g/mol
nH = 2, MH = 1.008 → 2.016 g/mol
Total molar mass = 74.092 g/mol
Nested parentheses are expanded before applying the summation, ensuring correct stoichiometry for hydrates and complex salts.
Full Description
Determining molecular weight is a foundational step in stoichiometry, solution preparation, gravimetric analysis, and analytical method validation. This calculator is designed for chemists, students, and laboratory technicians who need quick, accurate molar mass values without consulting printed tables. It parses complex inorganic and organic formulas, handles nested polyatomic groups, and reports both the total molar mass and the percentage contribution of each element so you can immediately use the data in quantitative calculations.
The atomic masses used by the tool are sourced from the latest IUPAC standard atomic weights (four decimal place precision for most elements) to balance accuracy with readability. Because the parser enforces chemical syntax, it provides instant feedback if a formula is malformed, helping beginners learn correct notation while giving professionals confidence that their inputs are interpreted correctly. The breakdown table is especially helpful when documenting calculations in laboratory notebooks or preparing regulatory compliance documents that require detailed composition reports.
Typical use cases
- Stoichiometric calculations: Convert grams to moles or vice versa for reactants and products.
- Solution preparation: Determine the mass required to prepare a desired molarity of solution.
- Quality control: Verify incoming raw material specifications against formulation requirements.
- Educational demonstrations: Show students how composition affects molar mass and percent composition.
- Regulatory reporting: Provide elemental breakdowns for safety data sheets or environmental submissions.
Why this tool stands out
- ✅ Robust parser: Handles parentheses and multiple element groups typical in inorganic chemistry.
- ✅ Detailed output: Presents molar mass alongside mass and percent contribution for each element.
- ✅ Updated data: Uses contemporary atomic weights for accurate calculations.
- ✅ Error guidance: Intuitive messages highlight syntax issues, reducing trial-and-error.
- ✅ Responsive design: Optimised for desktop and mobile use during lab work.
Frequently Asked Questions
Can the calculator handle hydrates or coordination complexes?
Yes. Use parentheses to group the hydrate or ligand and apply the appropriate subscript, for example CuSO4·5H2O can be entered as CuSO4(H2O)5.
Where do the atomic masses come from?
The calculator uses standard atomic weights published by IUPAC with four decimal precision, which is sufficient for most laboratory and educational purposes. For ultra-high precision work, consult CODATA values.
Why do I see an “unknown element” error?
Check that each element symbol is capitalised correctly (first letter uppercase, second letter lowercase if present). The parser only recognises valid IUPAC element symbols.
Does the calculator account for isotopic enrichment?
It assumes natural isotopic abundance. If you are working with isotopically labelled compounds, adjust the atomic masses manually or perform separate calculations for each isotopologue.
Can I export the elemental breakdown?
While the interface doesn't export directly, the table is formatted for easy copying into spreadsheets, lab reports, or ELN systems.