Stoichiometry (sometimes called reaction stoichiometry to distinguish it from composition stoichiometry)'s the calculation of quantitative (measurable) relationships of the reactants and products in a balanced chemical reaction (chemicals). It can be used to calculate quantities such as the amount of products that can be produced with the given reactants and percent yield. Etymology "Stoichiometry"'s derived from the Greek words στοιχεῖον (stoikheion… (More on Stoichiometry)