Atom Economy Calculator
Atom economy — the share of reactant mass that ends up in the desired product — and how it differs from percent yield.
Atom economy is the molar mass of the wanted product divided by the total molar mass of all reactants, times 100.
How the atom economy calculator works
Atom economy is the molar mass of the wanted product divided by the total molar mass of all reactants, times 100. It is fixed by the equation and cannot be improved by better technique.
That is what makes it different from yield. A reaction can run at 100% yield and still have 40% atom economy, because most of the mass leaves as by-products. Green chemistry cares about both, and the product is the honest figure.
Formula: atom economy = M(desired product) / Σ M(reactants) × 100
Worked examples
| Inputs | Atom economy | Note |
|---|---|---|
| Ethyl acetate from acetic acid and ethanol | 83.0286% | 83% — water is the only by-product |
| An addition reaction | 100% | 100% — nothing is lost |
| At 70% yield | 83.0286% | overall efficiency 58% |
FAQFrequently asked questions
What is atom economy?
The proportion of reactant mass that ends up in the product you actually want.
How is it different from yield?
Yield measures how much of the possible product you got; atom economy measures how much of the mass could ever have been product. A reaction can have perfect yield and terrible economy.
Which reactions score best?
Addition reactions, at 100% — every atom ends up in the product. Substitution and elimination always lose something.
Why does it matter?
Because the waste has to be separated and disposed of. In pharmaceutical manufacture, 25 to 100 kg of waste per kilogram of product is common.
Can I improve it?
Not by technique — only by choosing a different route. That is the point: it is a property of the chemistry, not the chemist.
Where these figures come from
- IUPAC — Standard atomic weights (2021 conventional values) — the molar-mass table
- NIST — CODATA 2018 fundamental physical constants — Avogadro constant, gas constant, speed of light
- NIST Chemistry WebBook — thermochemical data
- CSIRO — Australia's national science agency
Last checked: September 2026. Atomic masses are the IUPAC conventional values; constants are CODATA 2018; equations are the standard textbook forms.