Mole ratios, or molar ratios, are ratios determined from balanced chemical equations that can be used to predict the amount of product that will be formed, or the amount of reactant needed for the reaction to occur. Mole ratios can be expressed between reactants, products, or reactants and products.
For a chemical reaction in which two moles each of the reactants combine to create three moles of product, several mole ratios can be stated. For example, the mole ratio between the two reactants is 1:1. However, the mole ratio of either of the reactants to the product would be 2:3.