Atom Economy Calculator
Atom economy is a key green chemistry metric that quantifies how efficiently a reaction incorporates reactant atoms into the desired product. A reaction with low atom economy generates significant chemical waste even if it runs at 100% yield. The concept was introduced by Barry Trost and is now embedded in the twelve principles of green chemistry advocated by the ACS. Enter the molecular weight of the desired product (in g/mol) and the sum of molecular weights of all stoichiometric reactants to find atom economy as a percentage.
Atom economy formula
Atom Economy (%) = (MW of desired product / Sum of MW of all reactants) x 100
Multiply stoichiometric coefficients by the molecular weight of each reactant before summing when coefficients are not all 1. Only stoichiometric reagents are included; catalysts and solvents are excluded because they are recovered and reused.
Reaction types and typical atom economy
- Addition reactions (e.g., hydration, hydrogenation): up to 100% atom economy.
- Rearrangement reactions: 100% atom economy because all atoms rearrange into the product.
- Substitution reactions: moderate, because a leaving group is expelled.
- Elimination reactions: low, because a small molecule such as water is lost.
- Condensation reactions: moderate, loss of a small molecule per coupling step.
Atom economy: frequently asked questions
What is atom economy?
Atom economy measures what fraction of the mass of all reactants ends up in the desired product. It was introduced by Barry Trost in 1991 as a metric for green chemistry. A 100% atom economy means every atom of every reactant is incorporated into the target product with no waste.
What is the atom economy formula?
Atom Economy (%) = (Molecular weight of desired product / Sum of molecular weights of all reactants) x 100. Only stoichiometric molecular weights are used; the actual amounts reacted do not change the result.
How is atom economy different from percent yield?
Percent yield measures how much of the theoretical product was actually obtained in a given experiment. Atom economy is an inherent property of the balanced reaction equation and does not depend on how well the reaction was run. A reaction can have 100% yield but poor atom economy if most atoms go into by-products.
What is a good atom economy value?
Green chemistry targets the highest possible atom economy. Rearrangement and addition reactions often have 100% atom economy. Substitution reactions are moderate. Elimination reactions are low because a small molecule (e.g., water or HBr) is discarded. The ACS Green Chemistry Institute recommends maximising atom economy in reaction design.
Does catalyst mass count in atom economy?
Catalysts are not consumed, so they are not included in the standard atom economy calculation. Only stoichiometric reagents that appear in the balanced equation as reactants are summed in the denominator.
Official sources
- ACS Green Chemistry Institute: Twelve Principles of Green Chemistry.
- NIST Chemistry WebBook: Molecular weight data.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.