What Is a Molecular Weight Calculator?
This calculator computes the molecular weight (molar mass) of a chemical compound from its formula, by summing the atomic weights of every atom present — essential for stoichiometry, solution preparation, and general chemistry work.
How to Use the Molecular Weight Calculator
- Enter a chemical formula using standard notation (e.g., H2O, C6H12O6, CaCO3).
- View the total molecular weight and element-by-element breakdown.
Molecular Weight Formula
Worked Example
2 Hydrogen atoms: 2 × 1.008 = 2.016
1 Oxygen atom: 1 × 16.00 = 16.00
Total molecular weight: 2.016 + 16.00 = 18.02 g/mol
Understanding Your Results
Molecular weight (molar mass) tells you the mass of one mole of a compound, expressed in grams per mole (g/mol) — the conversion factor between mass and moles used throughout chemistry calculations, including molarity and stoichiometry.
Formula Notation Tips
- Use standard element symbols with correct capitalization (Na, not NA or na).
- Numbers directly follow the element they apply to (H2O, not H 2 O).
- Parentheses for grouped subscripts (like Ca(OH)2) are not supported in this simplified version — enter expanded formulas instead.
Frequently Asked Questions
The mass of one mole of a compound, calculated by summing the atomic weights of all atoms in its chemical formula, expressed in grams per mole (g/mol).
Multiply each element's atomic weight by the number of atoms of that element in the formula, then sum all the results.
They're essentially the same value expressed in the same units (g/mol) — 'molecular weight' is more commonly used for molecules, while 'molar mass' is a more general term also applying to ionic compounds.
This simplified version doesn't support parenthetical grouping (like Ca(OH)2) — enter the expanded formula (CaO2H2) instead for compounds with grouped subscripts.
It's the conversion factor between mass and moles, essential for stoichiometry calculations, solution preparation (molarity), and virtually all quantitative chemistry work.