The limiting reagent is the reactant that is entirely consumed in a chemical reaction, capping the amount of product that can form. This calculator identifies it by converting each reactant's mass to moles (using its molar mass), then dividing by its stoichiometric coefficient from the balanced equation — the reactant with the smallest result is the limiting reagent. All other reactants are in excess, and the calculator reports how much of each excess reagent remains unconsumed. For each product entered, the theoretical yield is calculated from the moles of the limiting reagent scaled by the stoichiometric ratio. An optional percent yield field compares your actual experimental yield to the theoretical maximum. This type of stoichiometry calculation is central to synthetic chemistry, chemical engineering, and any laboratory preparation involving a balanced chemical equation.