Molecular Weight Calculator

This calculator computes molecular weight by parsing a chemical formula into its constituent elements and counts, then summing atomic weight times count across every element — the same arithmetic you'd do by hand from a periodic table, automated against an internal table of atomic weights covering hydrogen through bismuth drawn from the IUPAC Commission on Isotopic Abundances and Atomic Weights' 2021 standard atomic weights report, the internationally recognized reference values chemists cite for this constant. Its formula parser reads capital-letter-plus-optional-lowercase element symbols followed by an optional subscript count (defaulting to 1 when no number follows), so "C6H12O6" is read as 6 carbons, 12 hydrogens, and 6 oxygens; it also normalizes Unicode subscript digits (like the ₂ in H₂O) into ordinary digits before parsing, so either notation works. Right now it drives from a fixed dropdown of common compounds — water, salt, glucose, sulfuric acid, caffeine, and a dozen others — each mapped internally to its formula string and run through the same parser.

Alongside the total molecular weight, it returns a full element-by-element table showing each element's atomic weight, atom count, mass contribution, and percentage of the total molecular mass, plus a pie chart of that mass composition — useful for seeing at a glance which atoms actually carry most of a molecule's weight (in glucose, for example, oxygen contributes a disproportionate share of the mass despite having fewer atoms than hydrogen). The most important thing to know about molecular weight itself: it is numerically identical, in different units, to molar mass — a value in g/mol tells you both the mass of a single molecule (in atomic mass units) and the mass of one mole, roughly 6.022×10²³ molecules, of that substance, which is exactly the conversion factor stoichiometry calculations rely on to move between grams and moles.