liminfoStoichiometry Calculator
Free web tool: Stoichiometry Calculator
Stoichiometry Calculator
Calculate molecular weight from a chemical formula. Supports parentheses like Ca(OH)2.
Molecular Weight
180.156 g/mol
| Element | Count | Atomic Mass | Subtotal | Mass % |
|---|---|---|---|---|
| C | 6 | 12.011 | 72.066 | 40.0% |
| H | 12 | 1.008 | 12.096 | 6.7% |
| O | 6 | 15.999 | 95.994 | 53.3% |
About Stoichiometry Calculator
The Stoichiometry Calculator computes the molecular weight of any chemical compound from its molecular formula. Enter a formula such as H2O, NaCl, C6H12O6, or Ca(OH)2, and the calculator instantly parses each element symbol, counts the atoms, looks up the standard atomic mass for each element, and sums the contributions to produce the total molar mass in grams per mole (g/mol).
This tool is used by chemistry students, laboratory technicians, pharmacists, materials scientists, and anyone who needs to quickly verify or calculate molecular weights. The parser handles nested parentheses — for example Fe2(SO4)3 — making it suitable for complex inorganic and organic compounds. The element breakdown table shows each element, its atom count, atomic mass, subtotal mass contribution, and its percentage share of the total molecular weight.
The calculator uses IUPAC standard atomic weights covering 46 elements from hydrogen (H, 1.008) through uranium (U, 238.029), including all common elements found in organic chemistry, biochemistry, and inorganic chemistry. Ten preset compounds (H2O, NaCl, C6H12O6, H2SO4, Ca(OH)2, C2H5OH, NH3, CO2, Fe2O3, C12H22O11) are provided as quick-start examples. All computation runs entirely in your browser with no data sent to any server.
Key Features
- Parses standard chemical formulas with element symbols and subscript numbers
- Full support for nested parentheses such as Ca(OH)2 and Fe2(SO4)3
- Displays molecular weight in g/mol to three decimal places
- Element-by-element breakdown table with count, atomic mass, and subtotal
- Mass percentage (%) calculated for each element in the compound
- Ten built-in preset compounds for common molecules as quick-start examples
- Real-time calculation — results update instantly as you type the formula
- Covers 46 elements including all common organic, inorganic, and biochemical elements
Frequently Asked Questions
What is stoichiometry and what does this calculator compute?
Stoichiometry is the branch of chemistry dealing with the quantitative relationships of reactants and products. This calculator focuses on the foundational step: computing molar mass (molecular weight) from a chemical formula, expressed in grams per mole (g/mol). Knowing the molar mass is essential for converting between mass and moles in reaction calculations.
How do I enter a chemical formula with parentheses?
Use standard chemical notation. Uppercase letters start a new element symbol, lowercase letters continue the same symbol, numbers indicate atom counts, and parentheses group repeated units with a multiplier. Examples: Ca(OH)2, Fe2(SO4)3, C2H5OH. The parser fully supports nested parentheses.
Why does the element table show a "mass %" column?
Mass percentage shows what fraction of the total molecular weight each element contributes. For example, in H2O the oxygen contributes about 88.8% and hydrogen about 11.2% of the 18.015 g/mol molar mass. This is useful for elemental analysis, determining empirical formulas, and understanding compound composition.
Which atomic masses does the calculator use?
The calculator uses the standard atomic weights published by IUPAC, which are based on the natural isotopic abundances of each element. For hydrogen: 1.008, carbon: 12.011, oxygen: 15.999, nitrogen: 14.007, and so on. These are the values used in standard chemistry textbooks and laboratory work.
Can I calculate the molecular weight of glucose (C6H12O6)?
Yes — glucose is one of the preset examples. C6H12O6 has a molecular weight of 180.156 g/mol: 6 carbons × 12.011 = 72.066, 12 hydrogens × 1.008 = 12.096, and 6 oxygens × 15.999 = 95.994, summing to 180.156 g/mol.
What elements are supported?
The calculator supports 46 elements: H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Ag, Sn, I, Ba, Pt, Au, Hg, Pb, and U, among others. These cover all elements commonly encountered in general, organic, and inorganic chemistry.
Is this calculator accurate enough for lab use?
The atomic masses used are the IUPAC standard atomic weights accurate to 3–5 significant figures, which is appropriate for most laboratory stoichiometry calculations. For the highest-precision analytical work, consult the most current IUPAC tables, as atomic weights are occasionally revised as measurement methods improve.
How is this different from a molecular formula calculator?
This calculator accepts molecular formulas (which describe the actual number of each atom in a molecule) and computes molar mass, elemental composition, and mass percentages. It does not handle empirical formulas or balanced chemical equations — it focuses specifically on the composition and mass analysis of a single compound from its formula.