Molecular Weight Calculator
Enter any chemical formula to calculate its molecular weight, molar mass, elemental composition percentages, and atom counts with 4-decimal precision.
Enter a chemical formula above to calculate molecular weight
Molecular Weight Calculator
A molecular weight calculator computes the sum of standard atomic weights for every atom in a given molecular formula. The molecular weight calculator on this page parses chemical notation β including parentheses, square brackets, and nested groups β to return molar mass in grams per mole (g/mol) and Daltons (Da) with 4-decimal precision.
The molecular weight calculator uses IUPAC 2021 standard atomic weights for all 118 elements. Molecular weight determination is a routine step in stoichiometry, elemental analysis, and mass spectrometry workflows. Researchers at laboratories supplied by Sigma-Aldrich, Thermo Fisher Scientific, and Merck use molecular weight values to prepare solutions, verify compound purity, and design high-throughput screening assays.
- Speed β instant results without server round-trips
- Precision β 4-decimal accuracy matching IUPAC 2021 standards
- Detail β full elemental breakdown with mass percentages
- Chemical formula parser (recursive descent)
- Atomic mass table (118 elements, IUPAC 2021)
- Calculation engine (molar mass + composition)
- Output display (mass, atoms, percentages)
Instant Molecular Weight Calculation
To calculate molecular weight, enter a chemical formula in the input field. The molecular weight calculator processes the formula character by character, identifies element symbols, resolves subscripts, and multiplies each element's standard atomic weight by its atom count. The result displays within milliseconds because the calculation runs in the browser.
This molecular weight calculation tool supports complex chemical structures written in standard notation, SMILES notation, and InChI (International Chemical Identifier) compatible strings. Databases such as PubChem and ChemSpider store molecular weight data for millions of compounds; this calculator replicates that lookup locally for any formula entered.
- Molecular weight in g/mol and Da
- Individual atomic mass contributions
- Mass percentage composition per element
- Total atom count across the formula
Molar Mass Calculation
Molar mass is the mass of one mole of a substance, expressed in g/mol. One mole contains exactly 6.022 Γ 10Β²Β³ particles β a number defined by the Avogadro constant (Nβ). Molar mass and molecular weight share the same numerical value; the difference is the reference frame. Molecular weight describes a single molecule in Daltons (Da) or atomic mass units (amu). Molar mass describes one mole of molecules in g/mol.
To calculate molar mass, multiply each element's standard atomic weight by its subscript count in the molecular formula, then sum all contributions. For water (HβO): Hydrogen contributes 2 Γ 1.0080 = 2.0160 g/mol and Oxygen contributes 1 Γ 15.9990 = 15.9990 g/mol. The molar mass of water is 18.0150 g/mol.
How to Use Molecular Weight Calculator
Calculate molecular weight for any chemical formula in 3 steps.
Enter a Chemical Formula
Type a formula using standard chemical notation β H2O, Ca(OH)2, K4[Fe(CN)6], or C6H12O6. The parser accepts parentheses, square brackets, and curly braces for nested groups. Software such as ChemDraw and chemical informatics tools like RDKit and Open Babel use this same notation. DrugBank compound identifiers can be converted to molecular formulas for input.
Molecular Weight Examples
Select a compound to see its molecular weight calculation broken down by element.
Molecular weight values appear in proteomics, metabolomics, and pharmaceutical research. Protein molecular weight calculators process amino acid sequences, and DNA molecular weight calculators compute nucleotide chain masses. This general-purpose molecular weight calculator handles small molecules and polymer repeating units.
Frequently Asked Questions
Common questions about molecular weight calculations, molar mass, and this calculator.