Stoichiometry is the calculation of relative quantities of reactants and products in chemical reactions. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equals the total mass of the products leading to the insight that the relations among quantities of reactants and products typically form a ratio of positive integers. Practically, this means that if the amounts of the separate reactants are known the amount of the product can be calculated. Conversely, if one reactant has a known quantity and the quantity of product can be empirically determined, the amount of the other reactants can be determined, also by calculation.

As seen in the image to the right, where the balanced equation is:

        4 + 2O
        2 → CO
        2 + 2H

1 1 1
Stoichiometric Compounds are those compounds which follow the Stoichiometry that means these chemical stoichiometric compounds with an elemental composition can be represent by a ratio of well-defined nnatural numbers and follow the Law of definite Proportions.