This free online molecular weight calculator instantly computes the molar mass of a chemical compound from its formula, including nested parentheses like Ca(OH)2. It shows a full element-by-element breakdown of each atom's contribution.
How to Use the Molecular Weight Calculator
- Type a chemical formula using standard element symbols and subscript numbers, such as H2O or C6H12O6.
- Use parentheses for grouped atoms with a multiplier, such as Ca(OH)2 or Mg3(PO4)2.
- Click "Calculate" to see the total molecular weight and a breakdown by element.
Frequently Asked Questions
The tool parses your formula into individual elements and their atom counts, looks up each element's atomic mass, multiplies by its count, and adds up all the contributions to get the total molar mass in grams per mole (g/mol).
Water (H2O) has a molecular weight of about 18.015 g/mol: 2 hydrogen atoms (about 1.008 each) plus 1 oxygen atom (about 15.999). Try it yourself by entering H2O above.
Yes. Parenthesized groups with a trailing multiplier are supported, such as Ca(OH)2 (calcium hydroxide) or Mg3(PO4)2 (magnesium phosphate).
Yes, it's completely free, works instantly in your browser, and requires no sign-up.