Atom Economy Calculator
Calculate atom economy: (molar mass of desired product × stoichiometric coefficient) ÷ total molar mass of all reactants × 100. A green chemistry metric. For education only.
How to use this tool
- Enter molar mass of desired product, stoichiometric coefficient of product and total molar mass of all reactants (sum of m×coeff) in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your atom economy and the full breakdown beneath it.
Atom economy is a green chemistry metric that measures how efficiently atoms from reactants are incorporated into the desired product:
Atom economy = (M_product × coeff) ÷ Σ(M_reactants × coeff) × 100%
A value of 100% means no atoms are wasted. By-products reduce atom economy. Rearrangement and addition reactions often have higher atom economies than substitution or elimination reactions.
For education only.
Formula
Atom Economy (%) = (Molar mass of product (g/mol) × Stoichiometric coefficient of product) ÷ Total molar mass of all reactants (g/mol) × 100
Waste (%) = 100 − Atom Economy (%)
Mass incorporated into product (g/mol) = Molar mass of product × Stoichiometric coefficient
How it works
Atom economy, a key green chemistry metric introduced by Barry Trost, measures how efficiently the atoms of the starting materials end up in the desired product. It is calculated by dividing the total formula mass of the target product (accounting for stoichiometry) by the sum of formula masses of all reactants, then multiplying by 100. A value of 100% means no by-products are generated. The calculation is theoretical and based on balanced stoichiometry; actual yield and reaction selectivity are separate considerations.
Worked example
Worked example — 100% atom-economy reaction
- Desired product molar mass = 92.094 g/mol, stoichiometric coefficient = 1.
- Total molar mass of all reactants = 92.094 g/mol (all atoms end up in product).
- Mass incorporated = 92.094 × 1 = 92.094 g/mol.
- Atom economy = 92.094 ÷ 92.094 × 100 = 100%.
- Waste = 100 − 100 = 0%.
Atom economy = 100%, waste = 0%, mass incorporated into product = 92.094 g/mol.
Key terms
- Atom economy
- The percentage of reactant atoms that are incorporated into the desired product; a measure of reaction efficiency in green chemistry.
- Stoichiometric coefficient
- The number in front of a species in a balanced chemical equation indicating the molar ratio in which it participates.
- By-product
- A substance formed in a chemical reaction alongside the desired product; high by-product formation lowers atom economy.
- Green chemistry
- A set of principles aimed at designing chemical processes that minimise the use and generation of hazardous substances.
- Molar mass
- The mass of one mole of a substance (g/mol); the sum of atomic masses of all atoms in a formula unit.
Frequently asked questions
- What is atom economy used for?
- It was introduced by Barry Trost (1991) as a measure of synthetic efficiency. High atom economy reactions waste fewer atoms and generate less chemical waste, making them preferable in green chemistry and industrial synthesis.
- What is the difference between atom economy and percent yield?
- Percent yield measures how much of the theoretical product you actually collected. Atom economy measures how much of the reactant mass ends up in the desired product regardless of yield. A reaction can have 100% yield but low atom economy if most reactant atoms end up in by-products.