About

Atom economy quantifies the fraction of reactant atoms that end up in the desired product. Proposed by Barry Trost in 1991, it is defined as the ratio of the sum of molecular weights of desired products to the sum of molecular weights of all reactants, expressed as a percentage. A reaction with 100% atom economy converts every atom of starting material into useful product with zero waste. Real industrial reactions rarely achieve this. Rearrangements and additions approach it; substitutions and eliminations do not. Failing to evaluate atom economy before scale-up risks generating kilograms of byproduct per kilogram of target compound, inflating disposal costs and regulatory burden.

This calculator accepts either direct molecular weights or chemical formulas. When a formula is entered (e.g., C₆H₁₂O₆), the tool parses element symbols and counts, then sums IUPAC 2021 standard atomic masses automatically. The metric assumes stoichiometric coefficients of 1 unless you adjust the molecular weight by the coefficient yourself. Note: atom economy does not account for yield, solvent, catalyst, or energy input. It is a theoretical ceiling on mass efficiency under perfect conversion.

Formulas

Atom economy expresses what fraction of the total reactant mass is incorporated into the desired product.

AE = ∑ MW_{desired products}∑ MW_{all reactants} × 100%

Where AE is atom economy in percent, MW_{desired products} is the sum of molecular weights of only the target products, and MW_{all reactants} is the sum of molecular weights of every reactant consumed. Molecular weight for a given formula is computed by parsing element - count pairs:

MW = n∑i=1 count_i × M_i

Where count_i is the number of atoms of element i in the formula and M_i is the IUPAC standard atomic weight of element i in g/mol. For example, H₂O yields 2 × 1.008 + 1 × 15.999 = 18.015 g/mol.

Reference Data

Reaction Type	General Scheme	Typical Atom Economy	Example	AE (%)
Rearrangement	A → B	100%	Claisen rearrangement	100
Addition	A + B → C	100%	Diels-Alder reaction	100
Condensation	A + B → C + H₂O	70 - 95%	Aldol condensation	85 - 92
Substitution (nucleophilic)	A + B → C + D	40 - 80%	Williamson ether synthesis	55 - 75
Elimination	A → B + C	30 - 70%	Dehydration of alcohols	40 - 65
Grignard + Ketone	RMgBr + R′COR″ → alcohol + MgBrOH	45 - 65%	Tertiary alcohol synthesis	50 - 60
Wittig reaction	Aldehyde + Ylide → Alkene + Ph₃PO	20 - 45%	Stilbene synthesis	30 - 40
Friedel-Crafts acylation	ArH + RCOCl → ArCOR + HCl	60 - 80%	Acetophenone synthesis	70 - 78
Suzuki coupling	ArX + ArB(OH)₂ → Ar-Ar + XB(OH)₂	50 - 70%	Biaryl synthesis	55 - 65
Esterification (Fischer)	RCOOH + R′OH → RCOOR′ + H₂O	75 - 95%	Ethyl acetate	83
Oxidation (KMnO₄)	Substrate + KMnO₄ → Product + MnO₂ + KOH	15 - 40%	Alcohol to carboxylic acid	20 - 35
Hydrogenation (catalytic)	Alkene + H₂ → Alkane	100%	Ethylene to ethane	100
Beckmann rearrangement	Oxime → Lactam	100%	Caprolactam (nylon-6)	100
Heck reaction	ArX + Alkene → Ar-Alkene + HX	60 - 80%	Cinnamate synthesis	65 - 75
Metathesis (olefin)	2 Alkene → 2 Alkene′	75 - 100%	Ring-closing metathesis	80 - 95

Frequently Asked Questions

Atom economy is a theoretical metric based solely on stoichiometry and molecular weights. It assumes 100% conversion and ignores solvent, catalyst, and excess reagent. Reaction yield measures actual mass of product obtained versus theoretical maximum. E-factor (kg waste / kg product) captures total waste including solvents and auxiliaries. A reaction can have 100% atom economy but 30% yield, or 40% atom economy but high yield with enormous E-factor. Use all three together for a complete sustainability profile.

Yes. If your balanced equation uses 2 mol of a reactant with MW = 58 g/mol, enter 116 g/mol (or enter the formula twice as separate rows). This calculator sums the MW values you provide directly. Each row represents one molar equivalent. For multi-mole species, either multiply the MW before entry or add duplicate rows.

Catalysts are regenerated during the reaction and do not appear in the overall stoichiometric equation. They are not consumed, so their mass is excluded from both numerator and denominator. However, in practice catalyst degradation, ligand loss, and metal leaching do contribute to waste. The E-factor metric captures these real-world losses.

There is no universal cutoff, but the American Chemical Society Green Chemistry Institute considers reactions above 80% atom economy favorable. Pharmaceutical manufacturing often operates at 20-40% AE due to complex multi-step syntheses. The 12 Principles of Green Chemistry (Anastas & Warner, 1998) list maximizing atom economy as Principle #2. Aim for addition and rearrangement reactions when possible.

Yes, provided you know the molecular weights of substrates and products. Enzymatic reactions often exhibit high atom economy because enzymes catalyze specific transformations with minimal byproducts. Enter cofactors (NAD+, ATP) as reactants only if they are consumed stoichiometrically rather than recycled. Water molecules produced or consumed must be included in the calculation.

This tool parses simple molecular formulas of the form Element-Count (e.g., C6H12O6, NaCl, H2SO4). It does not currently parse nested parentheses like Ca(OH)2 or hydrate notation like CuSO4·5H2O. For such compounds, enter the molecular weight directly in the MW field. Ca(OH)2 = 40.078 + 2×(15.999 + 1.008) = 74.093 g/mol.