Atom Economy Calculator

g/mol
Molar mass of the target product only.
g/mol
Sum of molar masses of all reactants in the balanced equation.
Chemistry

Calculate the atom economy of a reaction — the percentage of reactant mass that ends up in the desired product. Divide the molar mass of the target product by the total molar mass of all reactants and multiply by 100. A high atom economy means less material is wasted as by-products, a key idea in green chemistry.

Formula

Atom economy (%) = (Molar mass of desired product / Total molar mass of reactants) x 100
  • Atom economy (%) = (molar mass of the desired product ÷ total molar mass of all reactants) × 100.
  • Use the molar masses from the balanced equation, including the coefficients, so every atom on the reactant side is counted.
  • A reaction can have a high percentage yield yet a low atom economy if much of the reactant mass leaves as by-products.
  • Addition reactions, where all reactant atoms appear in the product, have 100% atom economy; substitution and elimination reactions are lower.

Example: product 78.11 g/mol from 108.14 g/mol reactants

Inputs
  • Desired product molar mass: 78.11 g/mol
  • Total reactants molar mass: 108.14 g/mol

Atom economy = (78.11 ÷ 108.14) × 100 ≈ 72.23%, meaning about 72% of the reactant mass ends up in the desired product and the rest becomes by-products.

Frequently asked questions

What is atom economy?
It is the proportion of reactant mass that becomes the desired product, expressed as a percentage. Higher atom economy means a more efficient, less wasteful reaction.
How is atom economy different from percentage yield?
Yield measures how much product you actually obtain versus the theoretical maximum, while atom economy measures how much of the reactant mass could ever end up in the product, even at 100% yield.
Which reactions have the highest atom economy?
Addition reactions, in which all the atoms of the reactants are incorporated into a single product, have an atom economy of 100%.
Why does atom economy matter in green chemistry?
Reactions with high atom economy generate less waste and use raw materials more efficiently, lowering both cost and environmental impact.
What molar masses should I enter?
Use the molar mass of the single desired product and the sum of the molar masses of every reactant in the balanced equation, including their coefficients.