What is atom economy — and why does it matter?

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Atom economy (AE), introduced by Barry Trost in 1991, measures what fraction of the atoms in your starting materials end up in the desired product. A reaction with high AE generates little intrinsic waste — regardless of how much product you actually isolate. It is a design-stage metric, calculated directly from the balanced equation before any experiment is run.

GoalMaximise the proportion of reactant atoms that become part of the desired product, approaching 100%.

WhyHigh AE means less inherent waste, lower raw-material costs, simpler separations, and a smaller environmental footprint.

HowFavour addition and rearrangement reactions; replace stoichiometric reagents with catalysts; eliminate unnecessary protecting groups and derivatisation steps.

The formula

$$\text{AE} = \frac{\sum MW_{\text{desired products}}}{\sum MW_{\text{all reactants}}} \times 100\%$$

Symbol	Term	Units
$\text{AE}$	Atom Economy	% (dimensionless; ideal = 100%)
$\sum MW_{\text{desired}}$	Sum of molar masses of desired product(s) × stoichiometric coefficients	g mol⁻¹
$\sum MW_{\text{reactants}}$	Sum of molar masses of all consumed reactants × stoichiometric coefficients	g mol⁻¹

Catalysts are excluded from the denominator — they are not consumed by the reaction. Stoichiometric coefficients from the balanced equation can be included when the reaction is written in its simplest whole-number ratio. By-products reduce AE but are listed for mass-balance context.

Typical AE by reaction type

Reaction type	Typical AE	Reason
Addition / Cycloaddition (e.g. Diels–Alder)	~100%	All reactant atoms incorporated into product
Rearrangement	~100%	Only bond rearrangement; no atoms lost
Catalytic hydrogenation	~100%	H₂ fully incorporated; catalyst not consumed
Substitution (S_N2, S_NAr)	50–80%	Leaving group expelled as waste
Condensation (e.g. esterification)	60–80%	Small molecule (H₂O etc.) lost as by-product
Elimination	40–70%	HX or H₂O by-product generated
Oxidation / Reduction (stoichiometric)	<50%	Heavy oxidant/reductant becomes waste

Strengths and limitations

Strengths

Calculable at the design stage — before any experiment is performed
Predictive: flags reactions where most atoms will become waste by design
Drives innovation — encourages catalytic, addition, and rearrangement chemistry
Aligns environmental and economic goals (less inherent waste = lower costs)
Widely accepted; easy to communicate to non-specialists

Limitations

Theoretical only — ignores actual yield and side-reaction by-products
Does not account for solvents, excess reagents, or workup materials
Treats all non-product atoms equally, regardless of toxicity or fate
A 100% AE reaction can still have a poor E-factor if large solvent volumes are used
Does not capture energy consumption or life-cycle impacts

AE in context: complementary green metrics

Metric	What it measures	Stage
Atom Economy (AE)	Theoretical fraction of reactant mass incorporated into the desired product (from balanced equation)	Design
% Yield	Fraction of theoretical product actually isolated	Experimental
E-factor	Mass of all waste per mass of product (all inputs, real scale)	Experimental
PMI (Process Mass Intensity)	Total mass of all inputs per mass of product; PMI = E-factor + 1	Experimental
RME (Reaction Mass Efficiency)	AE × yield × stoichiometric factor — combined practical efficiency	Both

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Experiment details

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Experiment / reaction name

Researcher(s)

Date

Lab / institution

Reaction type

Solvent

Temperature

Catalyst / additive

Reference / DOI

Notes

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Reactants

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Enter each consumed reactant with its molar mass and stoichiometric coefficient. Do not include catalysts — they are not consumed and should not appear in the AE denominator.

Compound name	Formula (optional)	MW (g mol⁻¹)	Coeff.	MW × n

Σ Reactant MW — g mol⁻¹ denominator of AE

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Products

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Add the desired product(s) first, then any by-products. Only desired-product MW contributes to the AE numerator; by-products are shown for mass-balance context. Use the Role dropdown to switch between desired and by-product.

Compound name	Formula (optional)	MW (g mol⁻¹)	Coeff.	Role	MW × n

Include stoichiometric coefficients in AE calculation

Σ Desired product MW — g mol⁻¹ numerator of AE

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Results (updates live)

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Atom Economy

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% (higher is better)

Σ Reactant MW

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g mol⁻¹ (denominator)

Desired Product MW

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g mol⁻¹ (numerator)

Wasted Mass (MW)

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g mol⁻¹

Atom Economy (higher is better)

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0%25%50%75%100% (ideal)

Reactant mass contributions

Product vs. by-product / waste

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Detailed breakdown & interpretation

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Compound	Role	Formula	MW (g mol⁻¹)	Coeff.	MW × n	% of Σ reactants	Visual
Enter reactants and at least one desired product above to see breakdown.

Interpretation & recommendations

Enter reactants and at least one desired product above to generate an interpretation.

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Save & load sessions

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Sessions are stored in your browser only. No data leaves your device.

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Export

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Export your atom economy calculation as a PDF report or CSV data file. PDF opens in a new tab and uses your browser's print function. CSV downloads directly.

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Where can I read more?

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References are sorted alphabetically by first author.

P. T. Anastas and J. C. Warner, Green Chemistry: Theory and Practice, Oxford University Press, 1998. ISBN 978-0-19-850698-0. — Original statement of the 12 Principles; atom economy is Principle 2.
C. Jiménez-González et al., Org. Process Res. Dev., 2011, 15, 912–917. DOI. — Defines PMI and places AE in the broader context of green metrics.
R. A. Sheldon, Pure Appl. Chem., 2000, 72, 1233–1246. DOI. — Atom efficiency and catalysis in organic synthesis; compares AE with E-factor.
B. M. Trost, Science, 1991, 254, 1471–1477. DOI. — The original paper introducing atom economy.
B. M. Trost, Angew. Chem. Int. Ed., 1995, 34, 259–281. DOI. — Atom economy as a challenge for organic synthesis; reaction-type analysis.

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Contributors

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Roles follow the CRediT taxonomy (Contributor Roles Taxonomy), adapted for educational software. Hover a contributor's name for a summary, or a column header for the definition of that role.

Contributor

This portal was built with the assistance of a large language model (Claude, Anthropic), which was used to generate and refine code, articulate and structure contributed ideas within the defined page format, and support iterative design decisions. All scientific content, conceptual frameworks, pedagogical choices, and final outputs were directed, reviewed, and verified by the contributors listed above.

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How do I cite this page?

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If you use this tool in teaching or published work, please cite the DodecaGreen portal as the source.

Reference

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Atom economy calculator.