Molecular Weight Calculator
Fast and accurate online tool for calculating compound molecular weight, supporting molecular formulas and SMILES input, widely used in chemical research, education and industrial applications.
Frequently Asked Questions
Enter a chemical formula (e.g., H2O, NaCl) or SMILES string, then click the calculate button to get precise molecular weight and elemental composition analysis.
Supports standard chemical formulas, SMILES strings, and complex compound formulas including organic compounds, inorganic salts, etc.
We use the latest atomic mass data with multi-decimal precision calculations that meet research and educational requirements.
Yes, supports complex organic compounds including polycyclic compounds, heterocyclic compounds, etc. Also supports SMILES format input.
Method, source and limitations
Method version: molar-mass-2.0- Calculation method
- Formula parser or RDKit SMILES parser with implicit hydrogens included.
- Data source
- RDKit periodic-table average and isotope masses.
- Assumptions and limitations
- Formula mode supports elements, nested groups, and hydrates; it does not interpret reaction text.
- Verification example
- H2O gives an average molar mass of about 18.015 g/mol.
Verified Calculator · Last validated: 2026-07-28
Result guidance
How does this tool calculate the result?
Formula parser or RDKit SMILES parser with implicit hydrogens included.
How should I interpret the result?
Formula mode supports elements, nested groups, and hydrates; it does not interpret reaction text.
How can I verify the result?
H2O gives an average molar mass of about 18.015 g/mol.