How this calculator works
Use the balanced reaction and include every stoichiometrically consumed reactant. Molar-mass mode multiplies each molar mass by its coefficient; mass mode accepts the corresponding theoretical masses directly. These are reaction-basis masses, not arbitrary experimental charges. Solvents and catalysts are excluded unless consumed in the balanced equation.
Formula
Atom economy = desired-product stoichiometric mass / total stoichiometric reactant mass. For molar masses, each contribution is coefficient x M.
Worked example
Reactants contributing 28 g and 2 g to a 30 g desired product have 100% atom economy. A 50 g desired product from 100 g stoichiometric reactants has 50%.
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Frequently asked questions
Is this percent yield?
No. Yield compares actual product with theoretical product; atom economy describes the balanced reaction.
Should excess reagent be included?
Use stoichiometric amounts for atom economy. Actual excess belongs in a process mass-efficiency metric.
Can atom economy exceed 100%?
No. A result above 100% signals inconsistent coefficients or missing reactants.