Molecular Weight Calculator — From a Chemical Formula

Molecular weight is the foundation for almost every quantitative task in chemistry, from weighing out a reagent in a research lab to dialing in a reaction on a manufacturing line, where a small error in mass can ripple into wasted material and off-spec product. The stakes are highest in pharmaceutical work, where the figure feeds directly into dosage calculations that affect patient safety and efficacy.

The tool reads a chemical formula by separating it into element symbols and their subscripts, expands groups in parentheses or brackets and hydrates written with a dot (CuSO4·5H2O), then looks each element up in a built-in table of about 55 common elements, from hydrogen to uranium, using the CIAAW (IUPAC) abridged standard atomic weights. A symbol missing from the table is reported rather than counted as zero. Multiplying every element's atomic weight by how many times it appears, and adding those products together, yields the molecular weight of the whole compound.

Capitalization carries meaning here: 'Co' is cobalt, while 'CO' is carbon monoxide, so the case of each letter changes the answer entirely. Parentheses matter too. 'Mg(OH)2' contains two hydroxyl groups, and an element written without a number, like oxygen in 'H2O', still carries an implied subscript of 1 that has to be counted.