Calculate the atom economy of a reaction — a measure of how efficiently reactant atoms end up in the desired product.
Enter the molecular weight and stoichiometric coefficient of each reactant and desired product. The calculator determines what fraction of reactant mass ends up in your desired product. Byproducts and waste are not included in the numerator — only the product(s) you actually want.
Atom Economy = (Σ MW of desired products × their coefficients) / (Σ MW of all reactants × their coefficients) × 100%
This metric was introduced by Barry Trost in 1991 as a measure of reaction efficiency from a green chemistry perspective. Unlike percent yield (which measures how much product you actually isolate), atom economy measures how much of the reactant atoms could theoretically end up in the desired product — it's an intrinsic property of the reaction itself.
Worked example: The Diels-Alder reaction of butadiene (MW 54.09) + ethylene (MW 28.05) → cyclohexene (MW 82.14) has atom economy = 82.14 / (54.09 + 28.05) × 100 = 100%. It's an addition reaction — every atom ends up in the product.
Contrast: A Grignard reaction or Wittig reaction often has atom economy below 50% because large leaving groups become waste. Rearrangement and addition reactions have the best atom economy; elimination and substitution reactions are typically worse.