Overview
What Is a Molecular Weight Calculator?
This tool calculates the molecular weight (molar mass) of a chemical compound by summing the atomic weights of all atoms in its formula.
Calculate the molecular weight of a chemical formula.
This tool calculates the molecular weight (molar mass) of a chemical compound by summing the atomic weights of all atoms in its formula.
Useful for stoichiometry problems, lab preparation, and general chemistry coursework.
Type a formula like H2O or NaCl.
The result updates automatically.
Sum the atomic weights of every atom in the formula, based on the periodic table.
They're essentially the same value, molecular weight is typically unitless (relative) while molar mass is expressed in g/mol.
Basic formulas without parentheses work best - complex structures like Ca(OH)2 may need to be entered as CaO2H2 for accurate calculation.
The calculator will not recognize unsupported symbols - double-check your element abbreviations.
Yes, molecular weight is a fundamental value needed for mole-based stoichiometry calculations.
Yes, chemical symbols follow standard capitalization (e.g., 'Co' for cobalt vs 'CO' for carbon monoxide).
Simple organic formulas work, though very complex structures may require careful formula entry.
No, calculations happen entirely in your browser.
Grams per mole (g/mol), the standard unit for molar mass.
Yes, completely free with no sign-up required.